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Atmel AVR Microcontroller discussion group.
[AVR club] pcb tester - Ayla - Mar 7 8:09:59 2007
hi everybody
I just joined this group & I need some clues for designing a pcb
tester with a microcontroller (AVR or PIC)
if you can help me I'd be thankful
thanks in advance
Aila
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
I just joined this group & I need some clues for designing a pcb
tester with a microcontroller (AVR or PIC)
if you can help me I'd be thankful
thanks in advance
Aila
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
Re: [AVR club] pcb tester - Zack Widup - Mar 7 8:18:26 2007
Hello Aila,
What do you want to do exactly? You need to be more specific.
Zack
On 7 Mar 2007, Ayla wrote:
> hi everybody
> I just joined this group & I need some clues for designing a pcb
> tester with a microcontroller (AVR or PIC)
> if you can help me I'd be thankful
> thanks in advance
> Aila
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
Re: [AVR club] pcb tester - David Kelly - Mar 7 9:09:09 2007
On Wed, Mar 07, 2007 at 07:17:08AM -0600, Zack Widup wrote:
>
> What do you want to do exactly? You need to be more specific.
>
> On 7 Mar 2007, Ayla wrote:
>
> > hi everybody
> > I just joined this group & I need some clues for designing a pcb
> > tester with a microcontroller (AVR or PIC)
> > if you can help me I'd be thankful
Sounds like a homework assignment. Was posted to more than one list.
What you want is a bunch of probes to contact the PCB under test. You
want to make sure all the appropriate probes are shorted to each other,
and not shorted to any other.
Thats all there is to it.
The hard part is being flexible so that the PCB design can be changed.
--
David Kelly N4HHE, d...@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
>
> What do you want to do exactly? You need to be more specific.
>
> On 7 Mar 2007, Ayla wrote:
>
> > hi everybody
> > I just joined this group & I need some clues for designing a pcb
> > tester with a microcontroller (AVR or PIC)
> > if you can help me I'd be thankful
Sounds like a homework assignment. Was posted to more than one list.
What you want is a bunch of probes to contact the PCB under test. You
want to make sure all the appropriate probes are shorted to each other,
and not shorted to any other.
Thats all there is to it.
The hard part is being flexible so that the PCB design can be changed.
--
David Kelly N4HHE, d...@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
Re: [AVR club] pcb tester - aila h - Mar 8 7:22:49 2007
Hi David
It’s not a homework in fact I have graduated from university a year ago . I just need quick & useful clues ,so I posted this to some lists.
I have thought of this board (bed of nails) that is full of pins that connects exactly to the soldered connections of my board & I made that.
but I have some troubles that I hope you can help me . In this case one of my troubles is that : in most circuits if there is a fault in circuit applying a voltage might be harmful for components .so how I can measure resistances , test rely & other components without applying voltage to board .
& I don’t know which multiplexer is suitable for this design?
If you can help me I’d be appreciate.
Thanks in advance
Aila
David Kelly wrote: On Wed, Mar 07, 2007 at 07:17:08AM -0600,
Zack Widup wrote:
>
> What do you want to do exactly? You need to be more specific.
>
> On 7 Mar 2007, Ayla wrote:
>
> > hi everybody
> > I just joined this group & I need some clues for designing a pcb
> > tester with a microcontroller (AVR or PIC)
> > if you can help me I'd be thankful
Sounds like a homework assignment. Was posted to more than one list.
What you want is a bunch of probes to contact the PCB under test. You
want to make sure all the appropriate probes are shorted to each other,
and not shorted to any other.
Thats all there is to it.
The hard part is being flexible so that the PCB design can be changed.
--
David Kelly N4HHE, d...@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.
---------------------------------
No need to miss a message. Get email on-the-go
with Yahoo! Mail for Mobile. Get started.
[Non-text portions of this message have been removed]
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
It’s not a homework in fact I have graduated from university a year ago . I just need quick & useful clues ,so I posted this to some lists.
I have thought of this board (bed of nails) that is full of pins that connects exactly to the soldered connections of my board & I made that.
but I have some troubles that I hope you can help me . In this case one of my troubles is that : in most circuits if there is a fault in circuit applying a voltage might be harmful for components .so how I can measure resistances , test rely & other components without applying voltage to board .
& I don’t know which multiplexer is suitable for this design?
If you can help me I’d be appreciate.
Thanks in advance
Aila
David Kelly
>
> What do you want to do exactly? You need to be more specific.
>
> On 7 Mar 2007, Ayla wrote:
>
> > hi everybody
> > I just joined this group & I need some clues for designing a pcb
> > tester with a microcontroller (AVR or PIC)
> > if you can help me I'd be thankful
Sounds like a homework assignment. Was posted to more than one list.
What you want is a bunch of probes to contact the PCB under test. You
want to make sure all the appropriate probes are shorted to each other,
and not shorted to any other.
Thats all there is to it.
The hard part is being flexible so that the PCB design can be changed.
--
David Kelly N4HHE, d...@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.
---------------------------------
No need to miss a message. Get email on-the-go
with Yahoo! Mail for Mobile. Get started.
[Non-text portions of this message have been removed]
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
Re: [AVR club] pcb tester - aila h - Mar 8 7:27:31 2007
Hi zack
I mean designing a bare board tester. but I have some troubles that I hope you can help me . In this case one of my troubles is that : in most circuits if there is a fault in circuit applying a voltage might be harmful for components .so how I can measure resistances , test rely & other components without applying voltage to board .
& I don’t know which multiplexer is suitable for this design?
If you can help me I’d be appreciate.
Thanks in advance
Aila
Zack Widup wrote:
Hello Aila,
What do you want to do exactly? You need to be more specific.
Zack
On 7 Mar 2007, Ayla wrote:
> hi everybody
> I just joined this group & I need some clues for designing a pcb
> tester with a microcontroller (AVR or PIC)
> if you can help me I'd be thankful
> thanks in advance
> Aila
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
I mean designing a bare board tester. but I have some troubles that I hope you can help me . In this case one of my troubles is that : in most circuits if there is a fault in circuit applying a voltage might be harmful for components .so how I can measure resistances , test rely & other components without applying voltage to board .
& I don’t know which multiplexer is suitable for this design?
If you can help me I’d be appreciate.
Thanks in advance
Aila
Zack Widup
Hello Aila,
What do you want to do exactly? You need to be more specific.
Zack
On 7 Mar 2007, Ayla wrote:
> hi everybody
> I just joined this group & I need some clues for designing a pcb
> tester with a microcontroller (AVR or PIC)
> if you can help me I'd be thankful
> thanks in advance
> Aila
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
Re: [AVR club] pcb tester - David Kelly - Mar 8 19:25:26 2007
On Thu, Mar 08, 2007 at 12:49:28AM -0800, aila h wrote:
> Hi David
> It?s not a homework in fact I have graduated from university a year
> ago . I just need quick & useful clues ,so I posted this to some
> lists. I have thought of this board (bed of nails) that is full of
> pins that connects exactly to the soldered connections of my board &
> I made that.
To the *soldered* connections? So this is not a bare PCB but a built
PCB?
> but I have some troubles that I hope you can help me . In this case
> one of my troubles is that : in most circuits if there is a fault in
> circuit applying a voltage might be harmful for components .so how I
> can measure resistances , test rely & other components without
> applying voltage to board . & I don?t know which multiplexer is
> suitable for this design?
Generally one does not want to apply external current to a built
circuit, don't want to drive the output of an unpowered logic chip or
CPU.
If sourcing TTL levels looking for shorts and opens on bare PCBs then a
1000 ohm resistor in series will never flow more than 5 mA on a 5 volt
system. No point in using more than 5 mA to test a trace anyway.
If your PCB is already built and powered you may be able to test most
of its function by probing logic levels without sourcing anything to
the board. If logic levels are not good enough you need to use the A/
D. Once again a 1000 ohm resistor in series can help limit potential
for damage and not significantly affect results. Presumably you will
test a known good board and compare others against those results. So
while a 1000 ohm resistor could affect accuracy of a "voltmeter" you
will always get the same readings when probing the same circuit if it
is behaving the same as the original.
74HC374's are one of my favorite interface chips. Can source 30 mA per
pin without harm. Enough to drive many 5V relay coils. Most AVR ports
have similar drive capability.
74HC374 is an 8 bit latch, you can put a bunch of these on a single 8
bit output port then connect each chip select to individual output lines
or use a 74HC138 on 3 output lines to drive chip selects on (8)
74HC374's.
On CPUs with external data buses the 74HC374 can be mapped directly into
the address space. Make your own "port".
The 74HC374 can be used for input pretty much the same way as for
output. Its just that a single part doesn't work both ways in the same
circuit.
There are similar chips to the 74HC374 which use shift register
input/output for parallel output/input.
--
David Kelly N4HHE, d...@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
> Hi David
> It?s not a homework in fact I have graduated from university a year
> ago . I just need quick & useful clues ,so I posted this to some
> lists. I have thought of this board (bed of nails) that is full of
> pins that connects exactly to the soldered connections of my board &
> I made that.
To the *soldered* connections? So this is not a bare PCB but a built
PCB?
> but I have some troubles that I hope you can help me . In this case
> one of my troubles is that : in most circuits if there is a fault in
> circuit applying a voltage might be harmful for components .so how I
> can measure resistances , test rely & other components without
> applying voltage to board . & I don?t know which multiplexer is
> suitable for this design?
Generally one does not want to apply external current to a built
circuit, don't want to drive the output of an unpowered logic chip or
CPU.
If sourcing TTL levels looking for shorts and opens on bare PCBs then a
1000 ohm resistor in series will never flow more than 5 mA on a 5 volt
system. No point in using more than 5 mA to test a trace anyway.
If your PCB is already built and powered you may be able to test most
of its function by probing logic levels without sourcing anything to
the board. If logic levels are not good enough you need to use the A/
D. Once again a 1000 ohm resistor in series can help limit potential
for damage and not significantly affect results. Presumably you will
test a known good board and compare others against those results. So
while a 1000 ohm resistor could affect accuracy of a "voltmeter" you
will always get the same readings when probing the same circuit if it
is behaving the same as the original.
74HC374's are one of my favorite interface chips. Can source 30 mA per
pin without harm. Enough to drive many 5V relay coils. Most AVR ports
have similar drive capability.
74HC374 is an 8 bit latch, you can put a bunch of these on a single 8
bit output port then connect each chip select to individual output lines
or use a 74HC138 on 3 output lines to drive chip selects on (8)
74HC374's.
On CPUs with external data buses the 74HC374 can be mapped directly into
the address space. Make your own "port".
The 74HC374 can be used for input pretty much the same way as for
output. Its just that a single part doesn't work both ways in the same
circuit.
There are similar chips to the 74HC374 which use shift register
input/output for parallel output/input.
--
David Kelly N4HHE, d...@HiWAAY.net
========================================================================
Whom computers would destroy, they must first drive mad.
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )
Re: [AVR club] pcb tester - vahid nikoonezhad - Jun 5 12:50:50 2007
Ayla
I just joined this group & I need some clues for designing a pcb
tester with a microcontroller (AVR or PIC)
if you can help me I'd be thankful
thanks in advance
Aila
_._,_.___
hi aila
i built a full trainer board (tester) for avr.each board 55$
if you want that call me
w...@yahoo.com
thanks
V.NIKOO
---------------------------------
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[Non-text portions of this message have been removed]
(You need to be a member of avrclub -- send a blank email to avrclub-subscribe@yahoogroups.com )