DC-DC Adjustable Step-down Module

Support Product Questions
1

I got the DC-DC Adjustable Step-down Module with the CV and CC features. The constant voltage works great, but when I turn the CC trimpot, I don’t think it is increasing the current limit. I am not sure if the trimpot is broken or not but every time I turn it there is a small click sound and I haven’t reached the turn limit yet.

Thanks for the help.

2

You’re probably at the end of the travel. Try turning it the other way. Also, to actually set the current limit you’ll need to short circuit the output (or at least have a very low impedance load) be careful though, as it’s a quick way to break things if you don’t have the current limit set to minimum first!

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3

What if I do not want the current limit? I want to power 4 servo’s from a 13v 2.5v power supply and limit it to 5v, however when a connect a servo to the outputs the led’s go from just blue to blue and red. Also the servo doesn’t move with a Pwm signal. What led’s should be on to start with to provide enough amps?

Thanks

4

Hi Oliver

You are at the end of travel. It does this to stop people breaking it (the pot).

Luca
All things being normal (don’t know about the Chinese) you should be able to turn the CC fully anticlockwise until it clicks and it should be Zero amps output. Zero volts too if you put a load on it but don’t worry about that. When turned fully clockwise until it clicks output Amps will be maximum and the volts will be whatever you set it to.

If you don’t want or need any current limiting feature simply turn the CC pot fully clockwise (until it clicks).
Cheers Bob

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5

I have turned the CC to the max and the green led turns on, and as soon as I connect the servo it flashes blue wile the servo moves a bit, then goes back to the green and the servo doesn’t move. I have tried this with the power supply and a Lipo battery however the same issue occurs. Do you have any ideas?

Thanks

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6

Hi Luca,

I’ve used these boards before, and I tested them with a power resistor and a benchtop power supply. I found that the blue LED lights up when there’s current draw, and the red LED lights up when it’s limiting the current with the CC pot. The green light should be on when it’s recieving power.

Are you sure your servo is being controlled correctly? Any idea of how much current it’s drawing?

-James

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7

Hi @James

I have turned the CC pot to the very end so there is no current limit, and I have also tested the board with other devices as well and here are the results:

Small 3v DC motor: The motor turns continuously without a problem and led stays green
5v led: Same brightness and led stays green

I am using a 9g servo and it should draw about 800mah when turning. I have also tried a different servo and it still has the same issue. I am sure the servo is being controlled correctly because when I connected the 5v and gnd to my Raspberry pico, the servo worked fine.

Luca,

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8

Hi Luca,

Do you have a multimeter on hand to measure the voltage available to the servo motor? Once you’ve confirmed the output voltage is holding within the operating range of the servo under load you could reconnect your meter to measure the current draw while the servo is loading the regulator.
If the PWM is correct and the larger servo is not turning then I’d be inclined to think either the current or voltage limiting was insufficient to supply the servo.

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9

Hi Trent,

I do have a multimeter and have set the voltage to around 5v, which is in the working range of the servo, and there is no drop in voltage when I connect the servo, and when I measure the current, it reads 250ma than goes to 0ma even with the servo still connected.

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