8 second timer with a momentary switch on a 80-100watt system

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aamorello415

Joined Aug 22, 2018
1
so here's the deal guys, i currently have a 7.4-8.2v (2 18650s wired in series) powered system that is activated using a momentary switch. the switch turns on a heater core and a small fan until the switch is no longer pushed. the heater core requires at least 11 amps to function properly, and it has come to my attention that the customers using the device won't have the wherewithal to let go of the button after 5-8 seconds. i was looking at using a 555 chip to try to cut power off after 5 seconds and then have the chip reset once the button is let go, but apparently the 555 can only output 200ma. I can tweak my power supply somewhat, possibly down to 5v, but i still need a minimum of 80 watts going into this heater core. i'm at a loss on how to accomplish this, although i have a feeling if i had any formal electrical training the answer would be much clearer. idiot proofing this system has been much harder than anticipated. i can't use fuses as this button is going to be pushed all night. thank you in advance for your help, my deadlines are coming up quick and i could really use the help.
 

blue_coder

Joined May 7, 2016
36
Hello aamorello,
You simply need to connect your timer circuit (555 or whatever) to the input of a solid state relay. The relay can then hapily switch your 8v @ 80w.
 

olphart

Joined Sep 22, 2012
107
Or a MOSFET w/driver {switching either high side (P-Ch) or low side (N-Ch)}.
If it's just simple on / off a special driver won't be necessary.
Keeping it all at 8V kinda begs for a logic level FET.
But the 555 will drive the gate just fine.
 
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