PWM with set modes for leds in small form factor

Thread Starter

brightguy

Joined Feb 2, 2019
7
Hello, I have an led project using 3-4 300ma leds. Currently they are wired in series and powered by an a23 battery inside of a cyalume industrial chemlight. Call it a rave stick if you want. I'm trying to incorporate pwm functionality without sacrificing the form factor as feel and weight is a priority. What's the smallest pwm module that's available or would I have to design a circuit? I also am trying to get the pwm modes (on, low power strobe, and off) controlled by a button and not a potentiometer, similar to what inova's microlights used to do. Any help would be appreciated. I have many more questions and I can provide more details if needed. Thank you for your time.
 

Sensacell

Joined Jun 19, 2012
3,432
Use a micro controller that has 3 in-built PWM engines.

The only other parts you need are FET's or transistors to drive the LED's
An A23 battery is totally inappropriate for 300 ma operation, have a look at the data sheet.
 

Attachments

danadak

Joined Mar 10, 2018
4,057
A small UP with a single PWM, and Capsense for buttons, maybe one external MOSFET
could do the job.

Coding would be fairly simple, and simple PCB layout would be straight forward.

The below example is one chip, only R's and LEDs and MOSFET external. Two buttons
and one slider for brightness control using capsense. These are done via traces/pads
on a flex PCB or regular PCB. No other HW needed to do this. This only uses a small
fraction of chip resources,. ADC SAR and onboard Vref used to monitor Battery V and
warn user via flashing LEDs battery needs replacement.

upload_2019-2-3_7-9-42.png


CHIP is PSOC 4 familiy, Cypress.

Note it would also be possible using the SAR, config it as 2 channel, to also implement
a battery charger in case you use a NiMh battery. That would require external
MOSFET to handle charging current.

Lots of possibilities.


Regards, Dana.
 
Last edited:

Thread Starter

brightguy

Joined Feb 2, 2019
7
Use a micro controller that has 3 in-built PWM engines.

The only other parts you need are FET's or transistors to drive the LED's
An A23 battery is totally inappropriate for 300 ma operation, have a look at the data sheet.
Thank you for the fast reply. I figured as much about the a23. They work but aren't as bright as they could be. I've looked at 555 ic but that's still way too big. What kind of micro controllers are smaller? I'll post some pictures further down in the thread to elaborate.
 

Thread Starter

brightguy

Joined Feb 2, 2019
7
Making something like this and cramming it onto the back of the battery holders instead of the round package, but running 3-4 300ma leds instead of a single 20ma led. I'm not familiar with what kind of ic that is.
 

Attachments

Thread Starter

brightguy

Joined Feb 2, 2019
7
A small UP with a single PWM, and Capsense for buttons, maybe one external MOSFET
could do the job.

Coding would be fairly simple, and simple PCB layout would be straight forward.

The below example is one chip, only R's and LEDs and MOSFET external. Two buttons
and one slider for brightness control using capsense. These are done via traces/pads
on a flex PCB or regular PCB. No other HW needed to do this. This only uses a small
fraction of chip resources,. ADC SAR and onboard Vref used to monitor Battery V and
warn user via flashing LEDs battery needs replacement.

View attachment 169302


CHIP is PSOC 4 familiy, Cypress.

Note it would also be possible using the SAR, config it as 2 channel, to also implement
a battery charger in case you use a NiMh battery. That would require external
MOSFET to handle charging current.

Lots of possibilities.


Regards, Dana.
Thank you for the reply. How small we talking for this ic? And is it possible to control with only one button?
 

djsfantasi

Joined Apr 11, 2010
9,156
I’m working on driving three LED strings with PWM, and everything (except the LEDs) fitting within 12mm x 20mm x 4 mm. I’m using an SMT ATTiny micro... like the ATTiny85
 
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