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Re: RESET circuit tweaks
Posted: 11 Nov 2018 22:18
by exxos
exxos wrote: 11 Nov 2018 22:11
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)
Re: RESET circuit tweaks
Posted: 11 Nov 2018 23:11
by Icky
exxos wrote: 11 Nov 2018 22:18
exxos wrote: 11 Nov 2018 22:11
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.
Re: RESET circuit tweaks
Posted: 11 Nov 2018 23:45
by Icky
Hmm - with 100nF and 470K white screen and no boot. Reset button stays on white screen no boot or flicker of reset.
Re: RESET circuit tweaks
Posted: 11 Nov 2018 23:51
by exxos
Icky wrote: 11 Nov 2018 23:45
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..
Re: RESET circuit tweaks
Posted: 12 Nov 2018 00:00
by Icky
exxos wrote: 11 Nov 2018 23:51
Icky wrote: 11 Nov 2018 23:45
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 :)
Re: RESET circuit tweaks
Posted: 12 Nov 2018 00:03
by exxos
Aye, doesn't seem like its going to behave :( wonder if the 555 circuit could be rejigged to give a inverted output :shrug:
Re: RESET circuit tweaks
Posted: 12 Nov 2018 00:10
by Icky
exxos wrote: 12 Nov 2018 00:03
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.
Re: RESET circuit tweaks
Posted: 12 Nov 2018 00:16
by exxos
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..
Re: RESET circuit tweaks
Posted: 12 Nov 2018 00:19
by Icky
exxos wrote: 12 Nov 2018 00:16
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.
Re: RESET circuit tweaks
Posted: 12 Nov 2018 00:27
by exxos
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..