one shot timer current draw

wfontjr

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i built two of the one shot timers, one draws 12.5 ma the other draws 4 ma, they both function correctly

im not sure if the tlc555's or the other componets are exactly the same cause radio shack around here is not too reliable on parts

question could a lower power 555 be the differnce in current or which other componets could be the most likely culprit

the higher draw timer when connected to a camera system kept draining the 1.2 ah 12 volt battery dead in two days

thanks
 



Tinhorn

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Are you sure they are both TLC555's,  a "555" (without the TLC) literally draws 10 times more current than the TLC555 ! ! !

I think you should increase the resistor connected to pins 6/7 to 1Meg and decrease the cap value off pin 6/7.  This resistor effects the overall "Idle" current a <LOT>

My 2 stage timer uses 1 meg at each stage and only draws .3 ma's (thats Point Three!)  For a 10 second Shutter (recommended) use the 1M and a 10uf cap.

Tinhorn
 

wfontjr

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thanks, looks like you nailed another one, one is definitely marked tlc555, the other one is not,

i was a little misleading on the 4ma draw, that was total draw ms20 + the one shot timer (this one for sure has the tlc) Is that high for a ms20 with a one shot?

thanks for the useful information
 

Tinhorn

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wfontjr,

My MS20 + 2stage timer draws 2.14 ma's total, which is how I figured you're using a lower value resistor on pins 6/7

I use 1M + 100uf cap for 2min delay at stage 1 and 1M + 10uf for 10 sec's shutter on stage 2

Tinhorn
 

wfontjr

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i bought the tlc555s today and replaced the 555, this dropped the current to around 2ma, on a 3 timer board i was playing with (was originally 24ma), thanks tinhorn another life saved

another question i tried an experiment, i may have violated a few tenets, on a one shot timer board i built for a video cam i replaced r1 with a 100k pot and c1 with a 1000uf cap, my thoughts were to vary the pot to get a 30 sec to 160 sec variable time on,

question is when i screwed the pot to the lowest setting it glowed red and smoked, it seems to work ok around the middle settings on up, any way to prevent the heat or is the idea screwy, i only used the middle leg (wiper?) and one of the other legs, is this the correct way to hook up a pot

this circuit pulled around 12ma idle which concerns me for use, i hope you are not crying at this point,

thanks
 

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