Re: Digest for sfanalogcircuits@googlegroups.com - 1 Message in 1 Topic
Mark Alexander
Group: http://groups.google.com/group/sfanalogcircuits/topics
Michael Shiloh <michaels...@gmail.com> Apr 07 03:38PM -0700
Hi!
Accuracy not at all important. It's for a noise maker.
We tried the Forrest Mims circuit using two 1458s but while the first
op-amp correctly generates a square wave, the subsequent op-amps fail to
integrate it to a triangle and then a sine wave.
http://ecelab.com/circuit-function-gen.htm
I had my student rebuild the circuit to reduce the chance of errors and
shorts, but no luck. I inspected it closely and it seems correct.
Any tips on fixing this appreciated, although we are also open to other
ideas. I rather like the old ICL8038 but these are unavailable and I
don't know what other single chip function generators exist.
M
Michael Shiloh
Artist, designer, tinkerer, teacher, geek
KA6RCQ
michaelshiloh.pbworks.com
www.teachmetomake.com
teachmetomake.wordpress.com
http://groups.google.com/group/teach-me-to-make
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Michael Shiloh
1) all outputs show a square wave
2) i'm checking with a very old 'scope
3) i think we've swapped chips with others, although none of them are
brand new .
Supply voltage is +- 8V or so, from battery.
On 04/08/2012 03:23 PM, Mark Alexander wrote:
> Hey Michael,
>
> I can offer a few questions and a few ideas on troubleshooting it:
>
> - is there any signal at all on the output of the triangle and sine
> op-amps?
> * If so, what?
> * If it's static, what voltage is it sitting at?
> - what does the input waveform to the second-stage (triangle) op-amp look
> like?
> * Is the square wave making it that far?
> * If so, is it swinging above and below the non-inverting input voltage
> (GND), or is it offset by some amount?
>
> If only the sine outputs were misbehaving that would make me suspect a bad
> chip or bad power/ground connection on the second chip, but since the
> square and triangle outputs are in the same chip and the square output is
> working, that narrows the possibilities:
>
> - recheck the component values
> - swap in some new caps/resistors to make sure none of them is broken
>
> There is nothing subtle about this circuit, so there isn't a whole lot that
> can go wrong. Recheck power, recheck connections& component values, swap
> in and out some parts, trace the signal through the circuit and see what
> point it's failing at. If you're only observing the outputs with one
> method (i.e. listening with an earphone), try another way of observing:
> use a sound-card oscilloscope. Or hook up an LED or light bulb. When
> you've already checked everything you can think of, shaking things up a
> little can unstuck the brokey.
>
> Happy debugging,
> mark
>
>
> On Sun, Apr 8, 2012 at 12:17 PM,<sfanalog...@googlegroups.com> wrote:
>
>> Today's Topic Summary
>>
>> Group: http://groups.google.com/group/sfanalogcircuits/topics
>>
>> - student needs simple circuit to generate sine, square, triangular
>> wave: suggestions or ideas for fixing what we have<#13693638c162e123_group_thread_0>[1 Update]
>>
>> student needs simple circuit to generate sine, square, triangular wave:
>> suggestions or ideas for fixing what we have<http://groups.google.com/group/sfanalogcircuits/t/592e06cab7f511db>
>>
>> Michael Shiloh<michaels...@gmail.com> Apr 07 03:38PM -0700
>>
>> Hi!
>>
>> Accuracy not at all important. It's for a noise maker.
>>
>> We tried the Forrest Mims circuit using two 1458s but while the first
>> op-amp correctly generates a square wave, the subsequent op-amps fail
>> to
>> integrate it to a triangle and then a sine wave.
>>
>> http://ecelab.com/circuit-function-gen.htm
>>
>> I had my student rebuild the circuit to reduce the chance of errors and
>> shorts, but no luck. I inspected it closely and it seems correct.
>>
>> Any tips on fixing this appreciated, although we are also open to other
>> ideas. I rather like the old ICL8038 but these are unavailable and I
>> don't know what other single chip function generators exist.
>>
>> M
>>
>> Michael Shiloh
>> Artist, designer, tinkerer, teacher, geek
>> KA6RCQ
>> michaelshiloh.pbworks.com
>> www.teachmetomake.com
>> teachmetomake.wordpress.com
>> http://groups.google.com/group/teach-me-to-make
>>
>>
>>
>> You received this message because you are subscribed to the Google Group
>> sfanalogcircuits.
>> You can post via email<sfanalog...@googlegroups.com>.
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>
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