RESET circuit tweaks

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exxos
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Re: RESET circuit tweaks

Post by exxos » Sun Nov 11, 2018 10:18 pm

exxos wrote:
Sun Nov 11, 2018 10:11 pm
What capacitor value do you have in at the moment 22uf ? and 1K ?
I think the problem is the switch isn't discharging the capacitor fast enough... even when it is, the reset pulse low is just to short...

Try something like 100nF and 470K any higher values on either and it will malfunction (according to simulation anyway)
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Re: RESET circuit tweaks

Post by Icky » Sun Nov 11, 2018 11:11 pm

exxos wrote:
Sun Nov 11, 2018 10:18 pm
exxos wrote:
Sun Nov 11, 2018 10:11 pm
What capacitor value do you have in at the moment 22uf ? and 1K ?
I think the problem is the switch isn't discharging the capacitor fast enough... even when it is, the reset pulse low is just to short...

Try something like 100nF and 470K any higher values on either and it will malfunction (according to simulation anyway)
I was using 47uF and 940R. I'll try 100nF and 470K as you mention.

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Re: RESET circuit tweaks

Post by Icky » Sun Nov 11, 2018 11:45 pm

Hmm - with 100nF and 470K white screen and no boot. Reset button stays on white screen no boot or flicker of reset.

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Re: RESET circuit tweaks

Post by exxos » Sun Nov 11, 2018 11:51 pm

Icky wrote:
Sun Nov 11, 2018 11:45 pm
Hmm - with 100nF and 470K white screen and no boot. Reset button stays on white screen no boot or flicker of reset.
Damn... Try 47k..
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Re: RESET circuit tweaks

Post by Icky » Mon Nov 12, 2018 12:00 am

exxos wrote:
Sun Nov 11, 2018 11:51 pm
Icky wrote:
Sun Nov 11, 2018 11:45 pm
Hmm - with 100nF and 470K white screen and no boot. Reset button stays on white screen no boot or flicker of reset.
Damn... Try 47k..
Its a crazy one this one trying to find the right combination.

This is going to be the last one tonight. Am all reset out today. Didn't get anywhere near my recap task today.

Last soldering iron job :)

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Re: RESET circuit tweaks

Post by exxos » Mon Nov 12, 2018 12:03 am

Aye, doesn't seem like its going to behave :( wonder if the 555 circuit could be rejigged to give a inverted output :shrug:
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Re: RESET circuit tweaks

Post by Icky » Mon Nov 12, 2018 12:10 am

exxos wrote:
Mon Nov 12, 2018 12:03 am
Aye, doesn't seem like its going to behave :( wonder if the 555 circuit could be rejigged to give a inverted output :shrug:
Yep 47K made no difference still white screen :(

Definitely feel like :headbang: with this circuit. I tried out so many combinations today.

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Re: RESET circuit tweaks

Post by exxos » Mon Nov 12, 2018 12:16 am

I will have a look for a better reset chip tomorrow.. There are things like the LP3470 , must be some chip out there which has a good drive current so can do away with the LS05 all together..
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Re: RESET circuit tweaks

Post by Icky » Mon Nov 12, 2018 12:19 am

exxos wrote:
Mon Nov 12, 2018 12:16 am
I will have a look for a better reset chip tomorrow.. There are things like the LP3470 , must be some chip out there which has a good drive current so can do away with the LS05 all together..
That would be great if that is the case. The less chips the better.

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Re: RESET circuit tweaks

Post by exxos » Mon Nov 12, 2018 12:27 am

http://www.ti.com/product/TPS3808/technicaldocuments

Looks good.. But output drive seems a bit wimpy :roll:

I guess a small MOSFET could be used to beaf it up.. Still smaller than a TTL chip..
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