Hello,
Novice here. I have a device I'm trying to control from an arduino Nano (can be either an Every or IOT). The device requires power at ~2v and 45 micro amps. I'm able to get the voltage down using a voltage devider I created with resistors, but my current is still way too high. Any suggestions?
Hi there,
Can we ask what exactly is the device you're trying to power?
Devices draw current, so you may be misinterpreting the specification.
Please post a link to the data sheet or product page of the device.
Unfortunately, I'm winging it. The product is found on amazon at this link:
All I know is that if I connect the output of the power supply to my multimeter I get the 2v and 24 micro amps. Again, sorry I'm a noob here.
PDLC smart films are usually powered by AC voltages, in the range of 40-70V 50-60Hz, with very low current flow.
Check the output of the tiny power supply that came with your sample.
As @jremington said, those smart films seem to be powered by higher AC voltages.
I see that the product you linked to comes with a driver circuit which takes two AA batteries, for ~3v. Is it the case that you want to use the Arduino to control the driver circuit, rather than the film directly?
If this is the case, you should have no issues with limiting current. As Jremington also pointed out:
Devices draw current
Consider that those AA batteries are not really a current controlled supply. The current is not limited by how much the batteries can put out, rather by how much the circuit wants to take. This is referred to as current draw.
Well that's helpful. Here an image of the power supply. I measured it (using the AC measurement on the multimeter and got ~20v from the two AA batteries). Any recommendations on next steps to control that from an arduino nano?
Measure the current drawn from the AA batteries by the power supply and tell us what you get.
While you're at it, could we get a picture of the underside of the driver circuit?
2.45 vdc (or 0.25 vac but I assume you want dc coming from the batteries). You'll see in the image I soldered the switch so it turns on as soon as power is provided (which I can quickly undo).
We need to know the current in mA drawn by the power supply from the 2xAA batteries.
If you have a multimeter, put it on the current scale (somewhere around 200 mA could be a place to start), and place the meter leads in series with one battery connection to the power supply. Observe polarity!
If the batteries are producing only 2.45 V, they are approaching the end of life.
You'll see in the image I soldered the switch so it turns on as soon as power is provided (which I can quickly undo).
Good to see that you've already taken care of that step! Would have been the next hurdle to overcome, after you look into the current draw.
The batteries are rechargable. I wasn't able to get a current reading for some reason but the device is operating.
The batteries are rechargable.
That would explain it. If they are NIMH type, they will only give 1.2V instead of 1.5V. I don't imagine this is an issue right now.
I wasn't able to get a current reading for some reason but the device is operating.
You need to connect the multimeter in-line with the power ("series") rather than across the terminals ("parallel")
Have a quick read here:
(Edit: I'll admit that was maybe not the best resource. Big diagrams though..)
I have an idea I'm going to try tomorrow using a voltage divider from my source 9v and a transistor switch. I'll let you know where I land but feel free to toss out any other ideas.
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