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I am doing some final work on a power supply and decoupling caps for
logic IC's (74HCTXXX)

Anyway, I have heard that tantalum caps may be excessively delicate
and fail impressively.

Size is an issue slightly. Smaller caps are better.

It seems that monolithic ceramic caps are smaller than ceramic disc
caps. Is one inferior to the other or better for certain purposes?

-Tony




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Tony, I should defer this to Don Kinzer as he is a better 'teacher'
than I.

However, there has been too much made out of this Tantalum capacitor
issue of 'exploding' when 'abused'. There is a good reason many
manufacture's reference designs as well as most commercical products
use them; they are small and have a fairly low ESR. Having said that,
if you have a bad design and abuse the cap, it will 'explode'... But
this is easy to overcome by knowing the environment you put them in
which includes testing.

Back to your application, with the 74HCTxxx family, just add a simple
0.1uf monolithic cap closely connected between VDD and GND. For
higher speed devices (ie: CPLDs, FPGAs, ASIC, etc) this can get more
complex...

- Tom

--- In basicx@basi..., "arhodes19044" <spamiam@c...> wrote:
> I am doing some final work on a power supply and decoupling caps
for
> logic IC's (74HCTXXX)
>
> Anyway, I have heard that tantalum caps may be excessively delicate
> and fail impressively.
>
> Size is an issue slightly. Smaller caps are better.
>
> It seems that monolithic ceramic caps are smaller than ceramic disc
> caps. Is one inferior to the other or better for certain purposes?
>
> -Tony


______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.


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> ... there has been too much made out of this Tantalum capacitor issue
of 'exploding' when 'abused'...

I agree the danger is minimal and occurs _only if the capacitor is
installed backwards_ and the supply is stiff enough to vaporize the
micro-short that chemically forms when the part is reverse-polarized, as
I understand it.

If the supply is small, or short-circuit protected, all that will
probably happen is a short circuit; I've had a number of them - each my
fault. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



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EEPROM endurance enhancement and PC keyboard interface appnotes at
http://groups.yahoo.com/group/basicx/files/ Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



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--- In basicx@basi..., "Tom Becker" <gtbecker@r...> wrote:
> PC keyboard interface appnotes ...

The code in the app note doesn't handle shift lock, num lock or the
numeric keypad, navigation keys (Page Up, etc.), Function keys or
any of the special keyboard keys like the "Windows" key, "WWW" key,
etc. Support for these is not too difficult to implement.

The clock signal may have a period between 60uS and 100uS. This may
be difficult to deal with in BasicX since the time to execute the
simple loop shown below is about 90uS on the non-P version of the BX-
24. For the P version it is about 66uS.

It is possible that an interrupt task could respond quickly enough
to read the data line. I haven't tried it so I don't know.

Call PutPin(12, 1)
Do
Register.PortC = Register.PortC Xor &H01
Loop

Don



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Hi all,
I have owned a BasicX for over a year now and done absolutely nothing with
it. So, I decided to build a small, mobile robot and experiment with
behavior based robotics. I choose the following parts to build my robot
with:

BasicX processor
Pololu Micro Dual Serial motor controller (
http://www.pololu.com/products/pololu/0410/ )
Pololu chassis and Tamiya dual gear box with 3V motors (
http://www.pololu.com/products/pololu/0250/rrc_cmb1.big.html )
The robot will have a couple of bump switches up front, a few LEDS for
headlights and a couple of photocells for light/dark sensing.
Pololu 5” round prototyping PCB (
http://www.pololu.com/products/pololu/0330/ )

Now for the question, what is my best option for powering the robot and
motors. Main battery will be 9V NiCd
1. Power the BasicX and electronics via 5V regulated power and run
unregulated power to the motors (I have run these motors off of 9V with no
problems)
2. Power the BasicX via unregulated power and use the regulated output of
the BasicX for electronics. Run the motors off of 5V regulated power.
3. Same as #2 but run the motors off of unregulated power.
4. Split the incoming 9V into a 5V regulator for the BasicX and electronics
and a separate 6V regulator for the motors [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 )

David, first I would use NiMh not NiCd. In this day and age I wonder
why NiCd are still in production... I could go on and 'babble' about
battery chemistry but I'll spare you ;-)

I would go with #4 if you really want to run the motor off of 6V
instead of 9V. The important thing here is to isolate the BX-24 and
other logic supply from the motor. I never use the BX-24 5V regulator
to supply external devices. When designing robotic controllers, I
always use a regulated supply to the H-Bridge to eliminate the
dependance on the battery voltage.

- Tom

--- In basicx@basi..., "David Culp" <dculp@c...> wrote:
> Hi all,
> I have owned a BasicX for over a year now and done absolutely
nothing with
> it. So, I decided to build a small, mobile robot and experiment
with
> behavior based robotics. I choose the following parts to build my
robot
> with:
>
> BasicX processor
> Pololu Micro Dual Serial motor controller (
> http://www.pololu.com/products/pololu/0410/ )
> Pololu chassis and Tamiya dual gear box with 3V motors (
> http://www.pololu.com/products/pololu/0250/rrc_cmb1.big.html )
> The robot will have a couple of bump switches up front, a few LEDS
for
> headlights and a couple of photocells for light/dark sensing.
> Pololu 5" round prototyping PCB (
> http://www.pololu.com/products/pololu/0330/ )
>
> Now for the question, what is my best option for powering the robot
and
> motors. Main battery will be 9V NiCd
> 1. Power the BasicX and electronics via 5V regulated power and
run
> unregulated power to the motors (I have run these motors off of 9V
with no
> problems)
> 2. Power the BasicX via unregulated power and use the regulated
output of
> the BasicX for electronics. Run the motors off of 5V regulated
power.
> 3. Same as #2 but run the motors off of unregulated power.
> 4. Split the incoming 9V into a 5V regulator for the BasicX and
electronics
> and a separate 6V regulator for the motors > [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 )

David, to follow up on my earlier 'babble', I forgot to mention the
importance of grounding. Take your Logic and Motor supply grounds to
the main supply ground. The battery pack in your case.

BTW, I have used Pololu's SMC02B motor controller and their SSC02A
servo contoller. The nice thing about this product line is that you
can share a simple serial line with different device IDs. I've posted
examples on my 'rather crude hacked HTML' web site at:

http://home.comcast.net/~tomhandley/bx-24/bx-24.html

- Tom

--- In basicx@basi..., "David Culp" <dculp@c...> wrote:
> Hi all,
> I have owned a BasicX for over a year now and done absolutely
nothing with
> it. So, I decided to build a small, mobile robot and experiment
with
> behavior based robotics. I choose the following parts to build my
robot
> with:
>
> BasicX processor
> Pololu Micro Dual Serial motor controller (
> http://www.pololu.com/products/pololu/0410/ )
> Pololu chassis and Tamiya dual gear box with 3V motors (
> http://www.pololu.com/products/pololu/0250/rrc_cmb1.big.html )
> The robot will have a couple of bump switches up front, a few LEDS
for
> headlights and a couple of photocells for light/dark sensing.
> Pololu 5" round prototyping PCB (
> http://www.pololu.com/products/pololu/0330/ )
>
> Now for the question, what is my best option for powering the robot
and
> motors. Main battery will be 9V NiCd
> 1. Power the BasicX and electronics via 5V regulated power and
run
> unregulated power to the motors (I have run these motors off of 9V
with no
> problems)
> 2. Power the BasicX via unregulated power and use the regulated
output of
> the BasicX for electronics. Run the motors off of 5V regulated
power.
> 3. Same as #2 but run the motors off of unregulated power.
> 4. Split the incoming 9V into a 5V regulator for the BasicX and
electronics
> and a separate 6V regulator for the motors > [Non-text portions of this message have been removed]


______________________________
Stellaris® MCU Family: New Parts, New Package, New Price.


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

> It is possible that an interrupt task could respond quickly enough...

That's the suggestion of that appnote (for a naked processor), of
course, but I think you're right; the BX-24 interrupt probably can't
respond soon enough. Appnote gone. Tom
Tom Becker
--... ...--
GTBecker@GTBe... www.RighTime.com
The RighTime Clock Company, Inc., Cape Coral, Florida USA
+1239 540 5700



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

--- In basicx@basi..., "tombhandley" <gr13tbs@c...> wrote:
> Back to your application, with the 74HCTxxx family, just add a simple
> 0.1uf monolithic cap closely connected between VDD and GND. For
> higher speed devices (ie: CPLDs, FPGAs, ASIC, etc) this can get more
> complex...
>
> - Tom Excellent. While I wanted to know the theory of the differences
between the two types, My application was for decoupling the power on
the logic ICs in my pulse detector section, as well as for a power
supply.

I did experience a blown tantalum last week. I definitely abused it.
I never knew that they are polarized. My clue should have been the
lead lengths.... I had a big one temporarily used as a decoupling
cap. Reverse polarity. It let go in about 5 minutes. Impressive.

-Tony




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