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Hi,

I'm trying to use a button, and I am completely confused.
When the button is pressed (closed), I want pin 11 to go HIGH.
Here is my current code:

Option Explicit
Dim sensor As Single
Dim groundAlt As Single
Public Sub Main()
Call PutPin(12,bxInputPullup)
Do
if(GetPin(12) = 1) Then
Call PutPin(11,1)
End If
Loop
End Sub

Even when the switch is open, the buzzer connected to pin 11 rings.
What's up? Does it have anything to do with the setup in the
project>>chip menu? What should pin12 be set as? Right now it is
"IN". I've tried every setting, and they all do as described above...
except "1". That one does nothing :(

Thanks!



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Change your code to
if(GetPin(12) = 0) Then

Your switch should connect between pin 12 and ground. By assigning it to bxInputPullup, it will show high unless the pin is connected to ground, which is done by pressing the switch.

You may also want to add an 'else' statement. Otherwise, pin 11 will go high and stay high after you let go of the button.

Regards,
Thad

"penguin.rocketry" wrote:
Hi,

I'm trying to use a button, and I am completely confused.
When the button is pressed (closed), I want pin 11 to go HIGH.
Here is my current code:

Option Explicit
Dim sensor As Single
Dim groundAlt As Single
Public Sub Main()
Call PutPin(12,bxInputPullup)
Do
if(GetPin(12) = 1) Then
Call PutPin(11,1)
End If
Loop
End Sub

Even when the switch is open, the buzzer connected to pin 11 rings.
What's up? Does it have anything to do with the setup in the
project>>chip menu? What should pin12 be set as? Right now it is
"IN". I've tried every setting, and they all do as described above...
except "1". That one does nothing :(

Thanks!

---------------------------------
Luggage? GPS? Comic books?
Check out fitting gifts for grads at Yahoo! Search.

[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Add the following line after your call putpin =(11,1) :

else
call putpin(11,0)
end if.

What you are doing is setting pin 11 high, but not setting it to low if
the condition on pin 12 is false. Also, there is an error in you if
statement,. Because you have a pullup on pin 12, I assume you are
switching it to ground. therefor your if statement should read if(
getpint(12) = 0) then

neil

penguin.rocketry wrote:

> Hi,
>
> I'm trying to use a button, and I am completely confused.
> When the button is pressed (closed), I want pin 11 to go HIGH.
> Here is my current code:
>
> Option Explicit
> Dim sensor As Single
> Dim groundAlt As Single
> Public Sub Main()
> Call PutPin(12,bxInputPullup)
> Do
> if(GetPin(12) = 1) Then
> Call PutPin(11,1)
> End If
> Loop
> End Sub
>
> Even when the switch is open, the buzzer connected to pin 11 rings.
> What's up? Does it have anything to do with the setup in the
> project>>chip menu? What should pin12 be set as? Right now it is
> "IN". I've tried every setting, and they all do as described above...
> except "1". That one does nothing :(
>
> Thanks!
>
>------------------------------------------------------------------------
>
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.476 / Virus Database: 269.11.2/933 - Release Date: 2/08/2007 2:22 p.m.
>
>


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Thanks for your help. Pullup is what is confusing me, i think.
When the switch is closed, 5V flows through it. When the switch is closed,
I want Pin 11 to output 5V.
Thanks!
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

The pullup is only programmed for INPUTS i.e switches and sensors. A
pullup is an internally programmable rsistor ( inside the BX) that is
connected to +5 when programmed on. Its value is about 120k.
When pin 11 goes high when programmed as an output ( which has nothing
to do with pullups), it will be at 5v. Be aware that it can only source
about 20 mA. If you are driving anything other than a LED or a small
piezo beeper, you musyt use a transistor to source more current.
neil;
Ian Cinnamon wrote:

> Thanks for your help. Pullup is what is confusing me, i think.
> When the switch is closed, 5V flows through it. When the switch is closed,
> I want Pin 11 to output 5V.
> Thanks!
>
> [Non-text portions of this message have been removed]
>
>------------------------------------------------------------------------
>
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.476 / Virus Database: 269.11.2/933 - Release Date: 2/08/2007 2:22 p.m.
>
>


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

If you're not familiar with the term 'pullup', it works like this:

With nothing connected to the pin, the voltage on the pin will
'float', meaning it could be seen as either a high or low signal by
the processor. In order to reduce this confusion, we typically
connect a high value resistor (10KOhm) between the pin and +5V. With
that connected, the processor always sees a high signal. To bring the
signal low, connect the button between the pin and ground. At the pin
you will now have 2 connections, one to the button, and one to the
resistor. The resistor can't flow enough current to produce the high
signal when the button is pressed, so pressing the button creates a
definite low. When the button is released, the pin returns to it's
default high position (the resistor 'pulls' the signal up).

The side effect is that the logic you use in your code needs to be
reversed, because the pin goes low when you press the button.
You code would then look something like this:

Option Explicit
Dim sensor As Single
Dim groundAlt As Single
Public Sub Main()
Call PutPin(12,bxInputPullup)
Do
If(GetPin(12) = 0) Then
Call PutPin(11,1)
Else
Call PutPin(11,0)
End If
Loop
End Sub

-Don

--- In b...@yahoogroups.com, "penguin.rocketry" wrote:
>
> Hi,
>
> I'm trying to use a button, and I am completely confused.
> When the button is pressed (closed), I want pin 11 to go HIGH.
> Here is my current code:
>
> Option Explicit
> Dim sensor As Single
> Dim groundAlt As Single
> Public Sub Main()
> Call PutPin(12,bxInputPullup)
> Do
> if(GetPin(12) = 1) Then
> Call PutPin(11,1)
> End If
> Loop
> End Sub
>
> Even when the switch is open, the buzzer connected to pin 11 rings.
> What's up? Does it have anything to do with the setup in the
> project>>chip menu? What should pin12 be set as? Right now it is
> "IN". I've tried every setting, and they all do as described above...
> except "1". That one does nothing :(
>
> Thanks!
>



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

I think I get it now. My BX24 was damaged somehow, so the replacement
is coming...
In the meantime, I eventually want to be able to fire a nichrome wire
from the BX24. I want to use the full "force" of the attached battery
(9V, 5A). To do this, which transistor should I use and how do I hook
it up? Thanks!

--- In b...@yahoogroups.com, "njepsen@..." wrote:
>
> The pullup is only programmed for INPUTS i.e switches and sensors. A
> pullup is an internally programmable rsistor ( inside the BX) that is
> connected to +5 when programmed on. Its value is about 120k.
> When pin 11 goes high when programmed as an output ( which has nothing
> to do with pullups), it will be at 5v. Be aware that it can only source
> about 20 mA. If you are driving anything other than a LED or a small
> piezo beeper, you musyt use a transistor to source more current.
> neil;
> Ian Cinnamon wrote:
>
> > Thanks for your help. Pullup is what is confusing me, i think.
> > When the switch is closed, 5V flows through it. When the switch is
closed,
> > I want Pin 11 to output 5V.
> > Thanks!
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >------------------------------------------------------------------------
> >
> >No virus found in this incoming message.
> >Checked by AVG Free Edition.
> >Version: 7.5.476 / Virus Database: 269.11.2/933 - Release Date:
2/08/2007 2:22 p.m.
> >
>


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

> ... to fire a nichrome wire from the BX24. I want to use the full
"force" of the battery...

That might be a great spot for an SCR, in the low side of the nichrome
load. A signal on its gate will latch it on until the wire fuses.

ISTM the fusing wire current must be less than the battery capability,
and the SCR must be able to handle the fusing current and the
open-circuit battery voltage. Easy, I'll bet.
Tom


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

I know a bit about electronics, but not everything... what's an SCR and
ISTM?
Thanks!

On 8/4/07, Tom Becker wrote:
>
> > ... to fire a nichrome wire from the BX24. I want to use the full
> "force" of the battery...
>
> That might be a great spot for an SCR, in the low side of the nichrome
> load. A signal on its gate will latch it on until the wire fuses.
>
> ISTM the fusing wire current must be less than the battery capability,
> and the SCR must be able to handle the fusing current and the
> open-circuit battery voltage. Easy, I'll bet.
>
> Tom
>
>
>

--
Ian
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

> ... ISTM?

Sorry. It Seems To Me.

An SCR, a Silicon Controlled Rectifier or Thyristor, is a three-terminal
diode that, once conducting, normally stays on until no forward current
flows through it. It's a latching DC switch. They (and a bipolar
cousin, the Triac) are most commonly used in AC phase control, like lamp
dimmers, essentially PWMing the AC line. You might search for SCR
applications to better understand the device. Here's one that will
handle 8A; US$0.67:
http://www.onsemi.com/PowerSolutions/product.do?id=C122F1

An SCR can be used as a DC switch with the caveat that you can't
normally turn it off after you've turned it on. That's ideal, ISTM, for
your application - if I understand your need. Are you severing a
release cord?
Tom


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Putting your name and nichrome wire together suggests you are launching
rockets with the BX. From a safety standpoint I would stay away from SCRs.
You could have a bad connection which would allow the SCR to latch and
slowly heat the nichrome until ignition some time after you would have
considered the motor a dud and commanded the BX to abort iginition. This
could be remedied by always removing the power source after a failed launch
but avoiding the SCR all together would be my suggestion.

On 8/4/07, Ian Cinnamon wrote:
>
> I know a bit about electronics, but not everything... what's an SCR and
> ISTM?
> Thanks!
>
> On 8/4/07, Tom Becker >
> wrote:
> >
> > > ... to fire a nichrome wire from the BX24. I want to use the full
> > "force" of the battery...
> >
> > That might be a great spot for an SCR, in the low side of the nichrome
> > load. A signal on its gate will latch it on until the wire fuses.
> >
> > ISTM the fusing wire current must be less than the battery capability,
> > and the SCR must be able to handle the fusing current and the
> > open-circuit battery voltage. Easy, I'll bet.
> >
> > Tom
> >
> >
> > --
> Ian
>
> [Non-text portions of this message have been removed]
>
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

The nichrome will actually set off a small pyrotechnic charge (this is for a
rocketry altimeter), which releases the parachute. Once the pyrotechnic
charge goes off, the nichrome will be broken, meaning an SCR is perfect.
Iwas thinking of a transistor but this sounds much better.
Also, for the SCR, the one you linked to only sells in bulk. Will this one
work:?
http://www.teccor.com/cgi-bin/r.cgi/en/prod_parts.html?PartID=15842&LFSESSION=U0RYyo9ILr
Also, which is the gate, cathode, and anode (K/G/A)?

Thanks!

On 8/4/07, Tom Becker wrote:
>
> > ... ISTM?
>
> Sorry. It Seems To Me.
>
> An SCR, a Silicon Controlled Rectifier or Thyristor, is a three-terminal
> diode that, once conducting, normally stays on until no forward current
> flows through it. It's a latching DC switch. They (and a bipolar
> cousin, the Triac) are most commonly used in AC phase control, like lamp
> dimmers, essentially PWMing the AC line. You might search for SCR
> applications to better understand the device. Here's one that will
> handle 8A; US$0.67:
> http://www.onsemi.com/PowerSolutions/product.do?id=C122F1
>
> An SCR can be used as a DC switch with the caveat that you can't
> normally turn it off after you've turned it on. That's ideal, ISTM, for
> your application - if I understand your need. Are you severing a
> release cord?
>
> Tom
>
>
>

--
Ian
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Putting your name and nichrome wire together suggests you are
launching rockets with the BX. From a safety standpoint, I would
stay away from SCRs. You could have a poor connection which would
allow the SCR to latch and slowly heat the nichrome until ignition
some time after you would have considered the motor a dud and
commanded the BX to abort iginition. This could be remedied by
always removing the power source after a failed launch, but avoiding
the SCR all together would be my suggestion. You could get away with
a simply relay from radio shack (make sure coil current draw does
not exceed max output from BX pins) otherwise it is fairly easy to
find power MOSFETs in the 5A class for $2 or so.

--- In b...@yahoogroups.com, "Ian Cinnamon" wrote:
>
> I know a bit about electronics, but not everything... what's an
SCR and
> ISTM?
> Thanks!
>
> On 8/4/07, Tom Becker wrote:
> >
> > > ... to fire a nichrome wire from the BX24. I want to use the
full
> > "force" of the battery...
> >
> > That might be a great spot for an SCR, in the low side of the
nichrome
> > load. A signal on its gate will latch it on until the wire fuses.
> >
> > ISTM the fusing wire current must be less than the battery
capability,
> > and the SCR must be able to handle the fusing current and the
> > open-circuit battery voltage. Easy, I'll bet.
> >
> > Tom
> >
> >
> > --
> Ian
> [Non-text portions of this message have been removed]
>



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Actually, when the nichrome wire heats, it heats instantly (it basically
melts). Also, the nichrome will only be fired at apogee (the highest point
of the rocket's flight. Even if the pyrodex doesn't go off, the nichrome
will melt itself into two pieces. So, unless the rocket experiences 2.1 Gs
(there is an acceleration switch) and hits a high altitude, nothing will
happen.

On 8/4/07, Russell Szczepaniec wrote:
>
> Putting your name and nichrome wire together suggests you are launching
> rockets with the BX. From a safety standpoint I would stay away from SCRs.
> You could have a bad connection which would allow the SCR to latch and
> slowly heat the nichrome until ignition some time after you would have
> considered the motor a dud and commanded the BX to abort iginition. This
> could be remedied by always removing the power source after a failed
> launch
> but avoiding the SCR all together would be my suggestion.
>
> On 8/4/07, Ian Cinnamon >
> wrote:
> >
> > I know a bit about electronics, but not everything... what's an SCR and
> > ISTM?
> > Thanks!
> >
> > On 8/4/07, Tom Becker > e.com>>
> > wrote:
> > >
> > > > ... to fire a nichrome wire from the BX24. I want to use the full
> > > "force" of the battery...
> > >
> > > That might be a great spot for an SCR, in the low side of the nichrome
> > > load. A signal on its gate will latch it on until the wire fuses.
> > >
> > > ISTM the fusing wire current must be less than the battery capability,
> > > and the SCR must be able to handle the fusing current and the
> > > open-circuit battery voltage. Easy, I'll bet.
> > >
> > > Tom
> > >
> > >
> > >
> >
> > --
> > Ian
> >
> > [Non-text portions of this message have been removed]
> >
> >
> > [Non-text portions of this message have been removed]
>
>
>

--
Ian
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

> ... Will this one work?
Probably, yes. I suspect most any small SCR will be fine if it can
handle the open-circuit supply voltage, the on current, and the gate
voltage and current can be supplied by the processor. Those parameters,
200v, 7.6A, 1.5v and 20mA max, look fine in that device, I think.
Tom



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

By the sounds of the application an untimely firing wouldn't really
endanger anybody so it isn't much of an issue. However, from an
explosives standpoint (my background) an SCR would never be worth
the risk. If somehow, there there is a faulty connection that
introduced excessive resistence to the firing circuit there is a
reasonable chance that the nichrome will not melt. However, because
the nichrome will complete the circuit from the SCR to the battery,
the SCR will latch (because the current to latch the SCR is
miniscule compared to the current to heat the nichrome). If the
faulty connection improves before the power is removed the nichrome
will heat and your pyro charge will fire. A less likely scenario
involves the faulty connection introducing enough resistance to
slowly heat the nichrome to the point that it fires the pyro charge
many minutes after it was supposed to.
--- In b...@yahoogroups.com, "Ian Cinnamon" wrote:
>
> Actually, when the nichrome wire heats, it heats instantly (it
basically
> melts). Also, the nichrome will only be fired at apogee (the
highest point
> of the rocket's flight. Even if the pyrodex doesn't go off, the
nichrome
> will melt itself into two pieces. So, unless the rocket
experiences 2.1 Gs
> (there is an acceleration switch) and hits a high altitude,
nothing will
> happen.
>
> On 8/4/07, Russell Szczepaniec wrote:
> >
> > Putting your name and nichrome wire together suggests you are
launching
> > rockets with the BX. From a safety standpoint I would stay away
from SCRs.
> > You could have a bad connection which would allow the SCR to
latch and
> > slowly heat the nichrome until ignition some time after you
would have
> > considered the motor a dud and commanded the BX to abort
iginition. This
> > could be remedied by always removing the power source after a
failed
> > launch
> > but avoiding the SCR all together would be my suggestion.
> >
> > On 8/4/07, Ian Cinnamon >
> > wrote:
> > >
> > > I know a bit about electronics, but not everything... what's
an SCR and
> > > ISTM?
> > > Thanks!
> > >
> > > On 8/4/07, Tom Becker 40rightime.com> > > e.com>>
> > > wrote:
> > > >
> > > > > ... to fire a nichrome wire from the BX24. I want to use
the full
> > > > "force" of the battery...
> > > >
> > > > That might be a great spot for an SCR, in the low side of
the nichrome
> > > > load. A signal on its gate will latch it on until the wire
fuses.
> > > >
> > > > ISTM the fusing wire current must be less than the battery
capability,
> > > > and the SCR must be able to handle the fusing current and the
> > > > open-circuit battery voltage. Easy, I'll bet.
> > > >
> > > > Tom
> > > >
> > > >
> > > >
> > >
> > > --
> > > Ian
> > >
> > > [Non-text portions of this message have been removed]
> > >
> > >
> > >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> > --
> Ian
> [Non-text portions of this message have been removed]
>



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

So a MOSFET is better? If so, would you mind recommending a good one?

Thanks

On 8/4/07, meenbombs wrote:
>
> By the sounds of the application an untimely firing wouldn't really
> endanger anybody so it isn't much of an issue. However, from an
> explosives standpoint (my background) an SCR would never be worth
> the risk. If somehow, there there is a faulty connection that
> introduced excessive resistence to the firing circuit there is a
> reasonable chance that the nichrome will not melt. However, because
> the nichrome will complete the circuit from the SCR to the battery,
> the SCR will latch (because the current to latch the SCR is
> miniscule compared to the current to heat the nichrome). If the
> faulty connection improves before the power is removed the nichrome
> will heat and your pyro charge will fire. A less likely scenario
> involves the faulty connection introducing enough resistance to
> slowly heat the nichrome to the point that it fires the pyro charge
> many minutes after it was supposed to.
>
> --- In b...@yahoogroups.com , "Ian Cinnamon"
> wrote:
> >
> > Actually, when the nichrome wire heats, it heats instantly (it
> basically
> > melts). Also, the nichrome will only be fired at apogee (the
> highest point
> > of the rocket's flight. Even if the pyrodex doesn't go off, the
> nichrome
> > will melt itself into two pieces. So, unless the rocket
> experiences 2.1 Gs
> > (there is an acceleration switch) and hits a high altitude,
> nothing will
> > happen.
> >
> > On 8/4/07, Russell Szczepaniec wrote:
> > >
> > > Putting your name and nichrome wire together suggests you are
> launching
> > > rockets with the BX. From a safety standpoint I would stay away
> from SCRs.
> > > You could have a bad connection which would allow the SCR to
> latch and
> > > slowly heat the nichrome until ignition some time after you
> would have
> > > considered the motor a dud and commanded the BX to abort
> iginition. This
> > > could be remedied by always removing the power source after a
> failed
> > > launch
> > > but avoiding the SCR all together would be my suggestion.
> > >
> > > On 8/4/07, Ian Cinnamon >
> > > wrote:
> > > >
> > > > I know a bit about electronics, but not everything... what's
> an SCR and
> > > > ISTM?
> > > > Thanks!
> > > >
> > > > On 8/4/07, Tom Becker > 40rightime.com> > > > e.com>>
> > > > wrote:
> > > > >
> > > > > > ... to fire a nichrome wire from the BX24. I want to use
> the full
> > > > > "force" of the battery...
> > > > >
> > > > > That might be a great spot for an SCR, in the low side of
> the nichrome
> > > > > load. A signal on its gate will latch it on until the wire
> fuses.
> > > > >
> > > > > ISTM the fusing wire current must be less than the battery
> capability,
> > > > > and the SCR must be able to handle the fusing current and the
> > > > > open-circuit battery voltage. Easy, I'll bet.
> > > > >
> > > > > Tom
> > > > >
> > > > >
> > > > >
> > > >
> > > > --
> > > > Ian
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > > >
> > > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> > >
> > >
> >
> >
> >
> > --
> > Ian
> >
> >
> > [Non-text portions of this message have been removed]
> >
>

--
Ian
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Here is one from Digikey:
http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=IRF510-ND

They are available from most suppliers. Your application doesn't
require anything special so I would just chose something capable of
handling 5A or more and 12V or more. At that current you will
probably want to get something in a TO-220 case because that would
probably be the easiest to work with. Because your full load will
only occur for milliseconds I wouldn't worry about adding any
additional heatsinks to the MOSFET.

--- In b...@yahoogroups.com, "Ian Cinnamon" wrote:
>
> So a MOSFET is better? If so, would you mind recommending a good one?
>
> Thanks
>
> On 8/4/07, meenbombs wrote:
> >
> > By the sounds of the application an untimely firing wouldn't really
> > endanger anybody so it isn't much of an issue. However, from an
> > explosives standpoint (my background) an SCR would never be worth
> > the risk. If somehow, there there is a faulty connection that
> > introduced excessive resistence to the firing circuit there is a
> > reasonable chance that the nichrome will not melt. However, because
> > the nichrome will complete the circuit from the SCR to the battery,
> > the SCR will latch (because the current to latch the SCR is
> > miniscule compared to the current to heat the nichrome). If the
> > faulty connection improves before the power is removed the nichrome
> > will heat and your pyro charge will fire. A less likely scenario
> > involves the faulty connection introducing enough resistance to
> > slowly heat the nichrome to the point that it fires the pyro charge
> > many minutes after it was supposed to.
> >
> > --- In b...@yahoogroups.com , "Ian
Cinnamon"
> > wrote:
> > >
> > > Actually, when the nichrome wire heats, it heats instantly (it
> > basically
> > > melts). Also, the nichrome will only be fired at apogee (the
> > highest point
> > > of the rocket's flight. Even if the pyrodex doesn't go off, the
> > nichrome
> > > will melt itself into two pieces. So, unless the rocket
> > experiences 2.1 Gs
> > > (there is an acceleration switch) and hits a high altitude,
> > nothing will
> > > happen.
> > >
> > > On 8/4/07, Russell Szczepaniec wrote:
> > > >
> > > > Putting your name and nichrome wire together suggests you are
> > launching
> > > > rockets with the BX. From a safety standpoint I would stay away
> > from SCRs.
> > > > You could have a bad connection which would allow the SCR to
> > latch and
> > > > slowly heat the nichrome until ignition some time after you
> > would have
> > > > considered the motor a dud and commanded the BX to abort
> > iginition. This
> > > > could be remedied by always removing the power source after a
> > failed
> > > > launch
> > > > but avoiding the SCR all together would be my suggestion.
> > > >
> > > > On 8/4/07, Ian Cinnamon >
> > > > wrote:
> > > > >
> > > > > I know a bit about electronics, but not everything... what's
> > an SCR and
> > > > > ISTM?
> > > > > Thanks!
> > > > >
> > > > > On 8/4/07, Tom Becker > > 40rightime.com> > > > > e.com>>
> > > > > wrote:
> > > > > >
> > > > > > > ... to fire a nichrome wire from the BX24. I want to use
> > the full
> > > > > > "force" of the battery...
> > > > > >
> > > > > > That might be a great spot for an SCR, in the low side of
> > the nichrome
> > > > > > load. A signal on its gate will latch it on until the wire
> > fuses.
> > > > > >
> > > > > > ISTM the fusing wire current must be less than the battery
> > capability,
> > > > > > and the SCR must be able to handle the fusing current and the
> > > > > > open-circuit battery voltage. Easy, I'll bet.
> > > > > >
> > > > > > Tom
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > > --
> > > > > Ian
> > > > >
> > > > > [Non-text portions of this message have been removed]
> > > > >
> > > > >
> > > > >
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > > >
> > > >
> > >
> > >
> > >
> > > --
> > > Ian
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> >
> > --
> Ian
> [Non-text portions of this message have been removed]
>



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

That would be good, but do any companies offer one with free samples (I
don't want to pay digikey $10 in shipping and handling for a $1 part)?
Thanks

On 8/4/07, meenbombs wrote:
>
> Here is one from Digikey:
> http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=IRF510-ND
>
> They are available from most suppliers. Your application doesn't
> require anything special so I would just chose something capable of
> handling 5A or more and 12V or more. At that current you will
> probably want to get something in a TO-220 case because that would
> probably be the easiest to work with. Because your full load will
> only occur for milliseconds I wouldn't worry about adding any
> additional heatsinks to the MOSFET.
>
> --- In b...@yahoogroups.com , "Ian Cinnamon"
> wrote:
> >
> > So a MOSFET is better? If so, would you mind recommending a good one?
> >
> > Thanks
> >
> > On 8/4/07, meenbombs wrote:
> > >
> > > By the sounds of the application an untimely firing wouldn't really
> > > endanger anybody so it isn't much of an issue. However, from an
> > > explosives standpoint (my background) an SCR would never be worth
> > > the risk. If somehow, there there is a faulty connection that
> > > introduced excessive resistence to the firing circuit there is a
> > > reasonable chance that the nichrome will not melt. However, because
> > > the nichrome will complete the circuit from the SCR to the battery,
> > > the SCR will latch (because the current to latch the SCR is
> > > miniscule compared to the current to heat the nichrome). If the
> > > faulty connection improves before the power is removed the nichrome
> > > will heat and your pyro charge will fire. A less likely scenario
> > > involves the faulty connection introducing enough resistance to
> > > slowly heat the nichrome to the point that it fires the pyro charge
> > > many minutes after it was supposed to.
> > >
> > > --- In b...@yahoogroups.com > ps.com>, "Ian
>
> Cinnamon"
> > > wrote:
> > > >
> > > > Actually, when the nichrome wire heats, it heats instantly (it
> > > basically
> > > > melts). Also, the nichrome will only be fired at apogee (the
> > > highest point
> > > > of the rocket's flight. Even if the pyrodex doesn't go off, the
> > > nichrome
> > > > will melt itself into two pieces. So, unless the rocket
> > > experiences 2.1 Gs
> > > > (there is an acceleration switch) and hits a high altitude,
> > > nothing will
> > > > happen.
> > > >
> > > > On 8/4/07, Russell Szczepaniec wrote:
> > > > >
> > > > > Putting your name and nichrome wire together suggests you are
> > > launching
> > > > > rockets with the BX. From a safety standpoint I would stay away
> > > from SCRs.
> > > > > You could have a bad connection which would allow the SCR to
> > > latch and
> > > > > slowly heat the nichrome until ignition some time after you
> > > would have
> > > > > considered the motor a dud and commanded the BX to abort
> > > iginition. This
> > > > > could be remedied by always removing the power source after a
> > > failed
> > > > > launch
> > > > > but avoiding the SCR all together would be my suggestion.
> > > > >
> > > > > On 8/4/07, Ian Cinnamon >
> > > > > wrote:
> > > > > >
> > > > > > I know a bit about electronics, but not everything... what's
> > > an SCR and
> > > > > > ISTM?
> > > > > > Thanks!
> > > > > >
> > > > > > On 8/4/07, Tom Becker > > > 40rightime.com> > > > > > e.com>>
> > > > > > wrote:
> > > > > > >
> > > > > > > > ... to fire a nichrome wire from the BX24. I want to use
> > > the full
> > > > > > > "force" of the battery...
> > > > > > >
> > > > > > > That might be a great spot for an SCR, in the low side of
> > > the nichrome
> > > > > > > load. A signal on its gate will latch it on until the wire
> > > fuses.
> > > > > > >
> > > > > > > ISTM the fusing wire current must be less than the battery
> > > capability,
> > > > > > > and the SCR must be able to handle the fusing current and the
> > > > > > > open-circuit battery voltage. Easy, I'll bet.
> > > > > > >
> > > > > > > Tom
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > --
> > > > > > Ian
> > > > > >
> > > > > > [Non-text portions of this message have been removed]
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > > [Non-text portions of this message have been removed]
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Ian
> > > >
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > >
> > >
> > >
> >
> >
> >
> > --
> > Ian
> >
> >
> > [Non-text portions of this message have been removed]
> >
>

--
Ian
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

I am not sure where to find a sample but Radio Shack (Ugh) has a
IRF510 MOSFET. However, it is only good for 3 amps but I suspect
it will still work for your application do to the extremely short
single pulse required of it. Otherwise, RS has a TIP120 transistor
that may work but I have no experience with that type of
transistor. There are many other people on this forum much better
versed in components than me. I yield my component selection advice
to anybody with a better idea or source.
--- In b...@yahoogroups.com, "Ian Cinnamon" wrote:
>
> That would be good, but do any companies offer one with free
samples (I
> don't want to pay digikey $10 in shipping and handling for a $1
part)?
> Thanks
>
> On 8/4/07, meenbombs wrote:
> >
> > Here is one from Digikey:
> > http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?
name=IRF510-ND
> >
> > They are available from most suppliers. Your application doesn't
> > require anything special so I would just chose something capable
of
> > handling 5A or more and 12V or more. At that current you will
> > probably want to get something in a TO-220 case because that
would
> > probably be the easiest to work with. Because your full load will
> > only occur for milliseconds I wouldn't worry about adding any
> > additional heatsinks to the MOSFET.
> >
> > --- In b...@yahoogroups.com , "Ian
Cinnamon"
> > wrote:
> > >
> > > So a MOSFET is better? If so, would you mind recommending a
good one?
> > >
> > > Thanks
> > >
> > > On 8/4/07, meenbombs wrote:
> > > >
> > > > By the sounds of the application an untimely firing wouldn't
really
> > > > endanger anybody so it isn't much of an issue. However, from
an
> > > > explosives standpoint (my background) an SCR would never be
worth
> > > > the risk. If somehow, there there is a faulty connection that
> > > > introduced excessive resistence to the firing circuit there
is a
> > > > reasonable chance that the nichrome will not melt. However,
because
> > > > the nichrome will complete the circuit from the SCR to the
battery,
> > > > the SCR will latch (because the current to latch the SCR is
> > > > miniscule compared to the current to heat the nichrome). If
the
> > > > faulty connection improves before the power is removed the
nichrome
> > > > will heat and your pyro charge will fire. A less likely
scenario
> > > > involves the faulty connection introducing enough resistance
to
> > > > slowly heat the nichrome to the point that it fires the pyro
charge
> > > > many minutes after it was supposed to.
> > > >
> > > > --- In b...@yahoogroups.com 40yahoogroups.com> > > ps.com>, "Ian
> >
> > Cinnamon"
> > > > wrote:
> > > > >
> > > > > Actually, when the nichrome wire heats, it heats instantly
(it
> > > > basically
> > > > > melts). Also, the nichrome will only be fired at apogee
(the
> > > > highest point
> > > > > of the rocket's flight. Even if the pyrodex doesn't go
off, the
> > > > nichrome
> > > > > will melt itself into two pieces. So, unless the rocket
> > > > experiences 2.1 Gs
> > > > > (there is an acceleration switch) and hits a high altitude,
> > > > nothing will
> > > > > happen.
> > > > >
> > > > > On 8/4/07, Russell Szczepaniec wrote:
> > > > > >
> > > > > > Putting your name and nichrome wire together suggests
you are
> > > > launching
> > > > > > rockets with the BX. From a safety standpoint I would
stay away
> > > > from SCRs.
> > > > > > You could have a bad connection which would allow the
SCR to
> > > > latch and
> > > > > > slowly heat the nichrome until ignition some time after
you
> > > > would have
> > > > > > considered the motor a dud and commanded the BX to abort
> > > > iginition. This
> > > > > > could be remedied by always removing the power source
after a
> > > > failed
> > > > > > launch
> > > > > > but avoiding the SCR all together would be my suggestion.
> > > > > >
> > > > > > On 8/4/07, Ian Cinnamon 40gmail.com>>
> > > > > > wrote:
> > > > > > >
> > > > > > > I know a bit about electronics, but not everything...
what's
> > > > an SCR and
> > > > > > > ISTM?
> > > > > > > Thanks!
> > > > > > >
> > > > > > > On 8/4/07, Tom Becker > > > > 40rightime.com> > > > > > > e.com>>
> > > > > > > wrote:
> > > > > > > >
> > > > > > > > > ... to fire a nichrome wire from the BX24. I want
to use
> > > > the full
> > > > > > > > "force" of the battery...
> > > > > > > >
> > > > > > > > That might be a great spot for an SCR, in the low
side of
> > > > the nichrome
> > > > > > > > load. A signal on its gate will latch it on until
the wire
> > > > fuses.
> > > > > > > >
> > > > > > > > ISTM the fusing wire current must be less than the
battery
> > > > capability,
> > > > > > > > and the SCR must be able to handle the fusing
current and the
> > > > > > > > open-circuit battery voltage. Easy, I'll bet.
> > > > > > > >
> > > > > > > > Tom
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > > --
> > > > > > > Ian
> > > > > > >
> > > > > > > [Non-text portions of this message have been removed]
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > > [Non-text portions of this message have been removed]
> > > > > >
> > > > > >
> > > > > >
> > > > >
> > > > >
> > > > >
> > > > > --
> > > > > Ian
> > > > >
> > > > >
> > > > > [Non-text portions of this message have been removed]
> > > > >
> > > >
> > > >
> > > >
> > >
> > >
> > >
> > > --
> > > Ian
> > >
> > >
> > > [Non-text portions of this message have been removed]
> > >
> >
> >
> > --
> Ian
> [Non-text portions of this message have been removed]
>



(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )

Will this work:
http://www.allelectronics.com/cgi-bin/item/BUZ71A/search/N-CHANNEL_POWER_MOSFET,_T0220_.html
Thanks

On 8/5/07, meenbombs wrote:
>
> I am not sure where to find a sample but Radio Shack (Ugh) has a
> IRF510 MOSFET. However, it is only good for 3 amps but I suspect
> it will still work for your application do to the extremely short
> single pulse required of it. Otherwise, RS has a TIP120 transistor
> that may work but I have no experience with that type of
> transistor. There are many other people on this forum much better
> versed in components than me. I yield my component selection advice
> to anybody with a better idea or source.
>
> --- In b...@yahoogroups.com , "Ian Cinnamon"
> wrote:
> >
> > That would be good, but do any companies offer one with free
> samples (I
> > don't want to pay digikey $10 in shipping and handling for a $1
> part)?
> > Thanks
> >
> > On 8/4/07, meenbombs wrote:
> > >
> > > Here is one from Digikey:
> > > http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?
> name=IRF510-ND
> > >
> > > They are available from most suppliers. Your application doesn't
> > > require anything special so I would just chose something capable
> of
> > > handling 5A or more and 12V or more. At that current you will
> > > probably want to get something in a TO-220 case because that
> would
> > > probably be the easiest to work with. Because your full load will
> > > only occur for milliseconds I wouldn't worry about adding any
> > > additional heatsinks to the MOSFET.
> > >
> > > --- In b...@yahoogroups.com > ps.com>, "Ian
>
> Cinnamon"
> > > wrote:
> > > >
> > > > So a MOSFET is better? If so, would you mind recommending a
> good one?
> > > >
> > > > Thanks
> > > >
> > > > On 8/4/07, meenbombs wrote:
> > > > >
> > > > > By the sounds of the application an untimely firing wouldn't
> really
> > > > > endanger anybody so it isn't much of an issue. However, from
> an
> > > > > explosives standpoint (my background) an SCR would never be
> worth
> > > > > the risk. If somehow, there there is a faulty connection that
> > > > > introduced excessive resistence to the firing circuit there
> is a
> > > > > reasonable chance that the nichrome will not melt. However,
> because
> > > > > the nichrome will complete the circuit from the SCR to the
> battery,
> > > > > the SCR will latch (because the current to latch the SCR is
> > > > > miniscule compared to the current to heat the nichrome). If
> the
> > > > > faulty connection improves before the power is removed the
> nichrome
> > > > > will heat and your pyro charge will fire. A less likely
> scenario
> > > > > involves the faulty connection introducing enough resistance
> to
> > > > > slowly heat the nichrome to the point that it fires the pyro
> charge
> > > > > many minutes after it was supposed to.
> > > > >
> > > > > --- In b...@yahoogroups.com > 40yahoogroups.com> > > > ps.com>, "Ian
> > >
> > > Cinnamon"
> > > > > wrote:
> > > > > >
> > > > > > Actually, when the nichrome wire heats, it heats instantly
> (it
> > > > > basically
> > > > > > melts). Also, the nichrome will only be fired at apogee
> (the
> > > > > highest point
> > > > > > of the rocket's flight. Even if the pyrodex doesn't go
> off, the
> > > > > nichrome
> > > > > > will melt itself into two pieces. So, unless the rocket
> > > > > experiences 2.1 Gs
> > > > > > (there is an acceleration switch) and hits a high altitude,
> > > > > nothing will
> > > > > > happen.
> > > > > >
> > > > > > On 8/4/07, Russell Szczepaniec wrote:
> > > > > > >
> > > > > > > Putting your name and nichrome wire together suggests
> you are
> > > > > launching
> > > > > > > rockets with the BX. From a safety standpoint I would
> stay away
> > > > > from SCRs.
> > > > > > > You could have a bad connection which would allow the
> SCR to
> > > > > latch and
> > > > > > > slowly heat the nichrome until ignition some time after
> you
> > > > > would have
> > > > > > > considered the motor a dud and commanded the BX to abort
> > > > > iginition. This
> > > > > > > could be remedied by always removing the power source
> after a
> > > > > failed
> > > > > > > launch
> > > > > > > but avoiding the SCR all together would be my suggestion.
> > > > > > >
> > > > > > > On 8/4/07, Ian Cinnamon > 40gmail.com>>
> > > > > > > wrote:
> > > > > > > >
> > > > > > > > I know a bit about electronics, but not everything...
> what's
> > > > > an SCR and
> > > > > > > > ISTM?
> > > > > > > > Thanks!
> > > > > > > >
> > > > > > > > On 8/4/07, Tom Becker > > > > > 40rightime.com> > > > > > > > e.com>>
> > > > > > > > wrote:
> > > > > > > > >
> > > > > > > > > > ... to fire a nichrome wire from the BX24. I want
> to use
> > > > > the full
> > > > > > > > > "force" of the battery...
> > > > > > > > >
> > > > > > > > > That might be a great spot for an SCR, in the low
> side of
> > > > > the nichrome
> > > > > > > > > load. A signal on its gate will latch it on until
> the wire
> > > > > fuses.
> > > > > > > > >
> > > > > > > > > ISTM the fusing wire current must be less than the
> battery
> > > > > capability,
> > > > > > > > > and the SCR must be able to handle the fusing
> current and the
> > > > > > > > > open-circuit battery voltage. Easy, I'll bet.
> > > > > > > > >
> > > > > > > > > Tom
> > > > > > > > >
> > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > > > --
> > > > > > > > Ian
> > > > > > > >
> > > > > > > > [Non-text portions of this message have been removed]
> > > > > > > >
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > > > [Non-text portions of this message have been removed]
> > > > > > >
> > > > > > >
> > > > > > >
> > > > > >
> > > > > >
> > > > > >
> > > > > > --
> > > > > > Ian
> > > > > >
> > > > > >
> > > > > > [Non-text portions of this message have been removed]
> > > > > >
> > > > >
> > > > >
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > Ian
> > > >
> > > >
> > > > [Non-text portions of this message have been removed]
> > > >
> > >
> > >
> > >
> >
> >
> >
> > --
> > Ian
> >
> >
> > [Non-text portions of this message have been removed]
> >
>

--
Ian
[Non-text portions of this message have been removed]


(You need to be a member of basicx -- send a blank email to basicx-subscribe@yahoogroups.com )