I'm looking for a circuit that will take in input voltage and match it, but allow for a lot more amps than a microcontroller can provide. I feel like this exists somewhere but after an entire evening of google, I can't seem to find a circuit that can provide the amps I need. It seems like the chips used to control voltage ate also low amps. (Keep in mind that I am new)
Does anyone have a circuit drawn out that could do what I imagine in the picture?
As I change the voltage using code in the microcontroller, I am hoping the magic circuit will match that voltage and provide plenty of amps to the load.
An op amp with a emitter follower, an example topology is below. Choose the op amp based on the speed you need and any offset errors that are acceptable. Power supply can be adapted to suit your output.
You haven;t said how you propose to get the analogue output fromthe Arduino.
I set the voltage on the pin analogWrite(pin, fade); // fade is 0 to 255
The load is a set of LEDs that I cannot change. They dim and brighten nicely between 2.3 and 3.3 volts. At fill load they draw 0.8 amps which would be too much for the arduino to handle.
The ESP32 DAC maximum output current limit is extremely hard to find, and does not seem to be published in the data sheet. According to this page, it is limited to about 12 mA, as are most of the digital pins, unless you specifically set high drive strength.
You should not plan on drawing that much, or the voltage will drop. The "magic circuit" is called a buffer amplifier, one example of which is given in post #3.
You can also buy power op amps specifically designed for high output currents. 1 Ampere is common, but the build will require a heat sink.
A cheapo opamp should be OK; based on the information given so far. Plus a power NPN transistor or a Darlington pair. With heat sink as advised.
A low pass filter to smooth the PWM output is easily added.
Nope I have a volt meter and no oscilloscope, but the voltage seems to go from 0-3.3 when I give it a value of 0-255. I suppose I could do some reading on this topic to see what my microcontroller does.
which means post a link to the datasheet of the LEDs.
LEDs are rated for a maximum current. Of course LEDs have a maximum voltage you should not exceed. But if you drive LEDs without any current-limiting resistorS
increasing the voltage for just 0,05V might exceed the maximum current going up to 200% of what the LED can stand.
And then the LEDs will wear out pretty quickly.
Or you need a current-limiting powersupply that is carefully adjusted.
You should post a schematic how you have wired the LEDs. Each LED should have their own current-limiting resistor. The reason is if one LED does not light up and draw current a commonly used single current-limiting resistor does not match anymore. ==> Current too high next LED destroyed. ==> current even higher ......
I don't have one ... this is a broken ring light. The controller is no longer working which I am looking to replace as a project with nano esp32
I see resistors in the light and i also started off using a resistor powered from a buck to test the different voltages. I know the voltage range of the lights because i was able to test it before the old controller stopped working all together.
Notes on the pics:
Click pic for high res
A marking, maybe model I could not find in google
The controller
The whole thing
A resistor on the ring light
The back of the ring light is aluminum, so I cannot see the circuit without delaminating it
It was powered from the circuit in the above pictures to an integrated usb cable that only provided power (no data). I believe the original died because it was barely enough for the current of the leds.... I'm hoping mine will last forever with bluetooth support and stuff
From the usb cable a + and -
Out to the leds a + and two - -
As someone pointed out above, the input to the light ring reads 5v
I assume they would cut the circuit on one of the two grounds in order to power the inner ring, outer ring or both rings.
From the user's view, this would provide a white/blue (cold) light, or a orange/yellow (warm) light, or a combination of the two colors.
It's to select or mix the two different whites. Cool white and/or warm white.
You can mix the two, to get the right colour temp. 3200-6000K.
This is common for a film/photo light.
You need a suitable 5volt/3A supply, and two logic level mosfets (or smd mosfet boards).
Common(+) is connected to 5volt(+), and the two (-) wires are switched to ground with the mosfets.
Leo..
I have a volt meter and no oscilloscope, but the voltage seems to go from 0-3.3 when I give it a value of 0-255. I suppose I could do some reading on this topic to see what my microcontroller does.
... this is a broken ring light. The controller is no longer working which I am looking to replace as a project with nano esp32
