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Need Help With Designing A Lithium Ion Battery Powered Delayed Power On Circuit

duckworth

May 11, 2017
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May 11, 2017
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Hello

I am trying to make a circuit powered by a 18650 lithium ion battery that will delay power on to a '3 watt bluetooth module' for connection to speakers

The Lithium Ion Battery when fully charged is around 3.7 volts which powers the bluetooth module reliably when connected directly

The bluetooth module can be found on aliexpress if you search for '3W bluetooth module' and sort by orders
I could post the link but it's really messy and long. I can post it if requested in a separate post

I've been looking at LM555 circuits but I want something that once the switch is closed it will delay power on for about three minutes and stay powered on for 105 minutes to forever, but will switch off immediately if the switch is opened.

I can connect modules together to build things but am getting confused by all the different types 555 of circuits and styles in which they can be used

I tried reading through all the circuits on this page but wanted something other than an 'oscillator' circuit
http://home.cogeco.ca/~rpaisley4/LM555.html#2

Would another type of timer circuit be better as I need the assembly to be really small?

Would this be the circuit to try first ?
http://www.learningaboutelectronics.com/Articles/555-timer-delay-before-turn-on-circuit.php


Thanks for your time for reading
and any help you can give

Rob
 
Last edited:

Bluejets

Oct 5, 2014
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You can buy ready-make 555 variable delay on modules from Ebay complete with relay output for a couple of dollars.
 

Audioguru

Sep 24, 2016
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The Lithium Ion Battery when fully charged is around 3.7 volts
No. A Lithium-ion 18650 cell is fully charged at 4.20V, is 3.7V when in storage or halfway in a discharge and is about 3.2V when it is almost dead and its load should be disconnected.
 

duckworth

May 11, 2017
2
Joined
May 11, 2017
Messages
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Thanks Bluejets most of the modules I could find on ebay are listed 5-12V ...
but I found one with dip switches for lower power applications
I found another timer that appears to use a crystal and resistor, but is mainly a black mound on a small PCB

Audioguru thanks too ... the 4.2V charged gives me a little more working room
 
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