Please Help (Fried Pins) I think i am slowly killing my STE

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dml
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Re: Please Help (Fried Pins) I think i am slowly killing my STE

Postby dml » Mon Sep 04, 2017 10:08 pm

Yes although the resistor values are wrong, especially the one on the left, for 22v. It will toast the IC.

The layout is ok though - for the simplest version of it.

AtariOwl
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Re: Please Help (Fried Pins) I think i am slowly killing my STE

Postby AtariOwl » Tue Sep 05, 2017 8:59 am

THe 22v shouldnt touch it.
Its not going to be connected across the rails. I still intend to use the GND rail and the separate rail that runs necxt to the GND which i would feed with 5v

Image

You can just about see the separate rail.

I assume we probably need to have some capacitors etc to protect the 4N25 ?

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dml
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Re: Please Help (Fried Pins) I think i am slowly killing my STE

Postby dml » Tue Sep 05, 2017 9:26 am

Yep ok - but I'd still calculate the resistor from the optoisolator datasheet vs 5v. Don't just copy something from the internet without checking stuff.

e.g. for 10mA to the optoisolator @ 5V:

5V / 0.010A = 500ohm.

But use the mA rating from the actual datasheet - somewhere between switching threshold and maximum rating.

The optoisolator should cope with typical noise from the motors but adding a small cap across it should help with noisy switching. Too large a value will suppress or prevent detection though.

If switching is still flaky (getting multiple on/off signals for a single event) you can debounce it by adding more bits to filter the switching. But see if it works at all first.

AtariOwl
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Re: Please Help (Fried Pins) I think i am slowly killing my STE

Postby AtariOwl » Thu Sep 07, 2017 11:27 am

Hi Doug

You are very right.

I now have a cheap oscilloscope on its way. I think this will help me check things a lot better than my simple DVM.

I can then approach this in a much less panicky way.
I have some caps of varying sizes now (up to 10uF) i can experiment with those too.
Also I now have some PC817s as well as 4n25s

AtariOwl
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Re: Please Help (Fried Pins) I think i am slowly killing my STE

Postby AtariOwl » Mon Oct 16, 2017 9:58 pm

Hi Everyone

Well after a series of setbacks, fried HDs, dead laptops etc. None connected with this issue, i returned to the problem at hand.

Regarding the timing i have a system working now using Opto Isolators

Specifically...

I am using
Image

Where
A is 470 Ohm
B is 1K8 Ohm
C is 1K8 Ohm

This seems to be running really well, very solid, but my numbers are somewhat arbitrary, how do i figure out what the best resistors will be? I've been trying to keep the numbers up to reduce current. But i just dont know.


OK now onto the Transformers
Image

I'm not at all sure how to attach them across the rails without short circuiting things?
Plus its DC, so i'm not sure what to do in that respect, i think in fact instead of being proper DC its a half wave thing which might mean we have effectively AC to transform, but i'm not sure.
I've torn apart an old dead VCR for coils so hopefully i have something to work with.

All advice gratefully received.


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