Hey everyone! I’m pretty new at trying to design my own circuits and need someone to double-check me and let me know if this little setup I’ve got going will work or not. It’s going to be integrated into a halloween costume. I’ve got a pretty basic understanding of electronics but I’m trying to expand it by working on little projects like this.
What I’m trying to accomplish:
I’ve got a force sensitive resistor that I would like to control the brightness of 4 small LEDs in unison. The harder I press on the FSR, the brighter the LEDs will get. It seems simple enough and I think I’ve got the code for it down.
I’m attaching the schematic, as I’m planning it now, in JPG format.
The LEDs I’m using are Vishay VLMU3100-GS08 Data sheet:Here
Main infos - the LEDs have a forward current of 20mA, forward voltage of 3.2V, they’re tiny, surface-mount numbers.
I’m using an Arduino Micro board. Currently I’m planning on using a 9v battery for power, though I may switch to AA’s if that’s highly recommended. I will be using it over the course of about 3 hours with the lights only being turned on in short bursts, probably once or twice every few minutes.
What I need more experienced Pros to tell me:
Can I actually power 4 of these LEDs at the same time from the 3.3v line with them wired in parallel, as shown? I understand the 3.3v line has a max of 40mA. This is where I’m fuzzy. Would all four lights being powered at once draw 80mA and burn out the controller?
If the 3.3v line won’t do it, would the 5v line?
If that won’t do it, would splitting them in groups of 2, one on the 3.3v and one on the 5v line work?
I’m planning on using PWM to dim the LEDs. This setup works great with the FSR to dim a single LED, but will the PWM still work now that I’m planning on running the signal through a transistor?
Is the diode between the LEDs and the collector necessary?
Assuming the parallel wiring setup will work, do I have the proper resistance? I’m using this LED resistor calculator to figure it out, I’m just hoping I’m putting the right numbers in.
Hopefully that’s not too much to ask! I genuinely appreciate any help. This should be a pretty cool effect for my costume if I can get it all to work.