Low Battery Warning Indicator

RE: Low Battery Warning Indicator

meangene1 — Sun, 23 Oct 2022 22:27:28 GMT

I got this circuit to basically function as described but had to use 6.2K for R2 along with12K for R1 to have a Vcutoff of 3.2V work properly. I calculated that a value of 10K for R2 and ~36k for R1 should work, but that didn't work on the breadboard. I am using the same parts as those in the example, except for substituting a PN2907 for the BC557. Any thoughts as to what's going on? Thanks.

RE: Low Battery Warning Indicator

phoenixcomm — Tue, 09 Feb 2021 19:50:28 GMT

[mention:b0bc65b9ecdc4307bd967592f00e340a:e9ed411860ed4f2ba0265705b8793d05] my analog knowledge is very limited. Great Job.

~~Cris

RE: Low Battery Warning Indicator

BigG — Mon, 08 Feb 2021 20:17:38 GMT

Hi Shabaz

Your blog looks very interesting.

I'm looking to create a wearable device with something like an ARM Cortex M0 device, which is powered directly with a 3V coin cell battery (CR2032). One feature I want to add is low battery voltage indication.

So, I was wondering if this circuit is suitable for such a design. For example, is the quiescent current of this circuit suitable and what about the current when the LED is actually on or flashing due to low voltage (surely it will drain battery even faster etc.)

Also what alternatives or tweaks are there (I know there is the standard voltage divider option using 100k resistors etc. to keep quiescent current low as possible and ensure ADC sample speed decent).

For example I came across this document using a CMOS comparator - but then thought that this is probably only valid if using an LDO.

https://www.maximintegrated.com/en/design/technical-documents/app-notes/1/1872.html

Any insight / pearls of wisdom greatly appreciated. Want to keep it simple as possible with minimal MCU processing.

Thanks

Colin

RE: Low Battery Warning Indicator

DAB — Tue, 22 Sep 2020 18:29:51 GMT

Very nice circuit.

DAB

RE: Low Battery Warning Indicator

genebren — Tue, 22 Sep 2020 15:11:33 GMT

Very cool designs! I have used the TL431 as a reference, but never as a control element. This was a great opportunity to learn something new and refresh my existing transistor and op-amp knowledge.

RE: Low Battery Warning Indicator

Fred27 — Tue, 22 Sep 2020 08:39:08 GMT

It's too easy to just use a microcontroller these days. It's nice to see a well designed circuit using analog electronics.

RE: Low Battery Warning Indicator

navadeepganeshu — Tue, 22 Sep 2020 06:51:35 GMT

Well depicted.

I always love these kind of basic highly functional op-amp circuit applications and this is well explained. I feel, all challenges can be encountered and exiting applications can be created just from the op-amps.

RE: Low Battery Warning Indicator

jw0752 — Tue, 22 Sep 2020 04:18:09 GMT

Hi Shabaz,

Great spin off of the Amplifier Blog. You are providing lots of building blocks for anyone who likes to imagine and build their own projects.

John