Hi guys, I am trying to control a 24v pump using a PWM pin of my Arduino UNO.
The Ardunio is connected to 12v dc power, and this is split through a 24v boost regulator (this is the model).
As the boost regulator is variable, it is set using a pot, which I used a multimeter to ensure was set to the required 24v. However, when I then connect everything, the input and output of the boost regulator then both go down from 12v & 24v to essentially zero. I assume they are being fried somehow but I'm not sure why. I always ensured the input voltage was within the 1.5-16v range, and less than the 24v output.
The pump has a DC input, a DC return and a DC speed control (1-5V).
I have drawn a circuit diagram below to illustrate, any help would be greatly appreciated!
The boost regulator should be good up to an output of 2A but I hadn't thought properly about not having enough power, I was just thinking of the currents - a silly mistake from me there.
I think maybe a buck regulator to step down from 24v may be better instead, or using a 12v 2A dc supply.
Please read the specs carefully:
Max INPUT CURRENT = 2A.
So you feed it with 12V, it'll only be able to output 24V @1A assuming 100% efficiency. In reality it'll be a bit less; probably around 850mA. This means that it'll juuuuuust work to keep the pump running, but the converter may not survive having to start the pump repeatedly as it'll have to source a much larger current during startup. In a PWM scenario this may be a major concern.
In general, stepping down works a little better than stepping up. So in this case I'd certainly go with a 24V PSU and a step down for your Arduino. The main reason this will work better is because the Arduino only consumes a tiny bit of power compared to the pump (by itself it won't draw even the 100mA of the current range on your whiteboard illustration), so the conversion losses (24V -> 12V) are much less than if you're stepping up the 12V Arduino power supply to 24V for the pump.
Thank you for such a detailed reply. My only concern (and why I initially opted to boost the voltage), is I will be taking temperature measurements and it is my understanding that bucking voltage will produce more excess heat? Also, do you think a 12v, 3A supply would work?
Firstly, make your temperature measurement independent of the power supply temperatures unless that's the temperature you want to measure. So mount the temperature sensor(s) in such a way that they aren't being heated by your power supply.
Secondly, the dissipation in the power supply is a function of the power draw and its efficiency. In the setup I proposed (24V supply with step-down for the Arduino), the overall efficiency will virtually certainly be higher than in your initial proposal, so less overall heat generated. You can further limit heat generation by (1) picking an efficient power supply and (2) over-dimensioning the power supply. To an extent these two approaches go counter to each other as conversion efficiencies tend to be higher at loads closer to the maximum ratings of a power supply (rule of thumb, more or less, YMMV), but generally speaking if you're going to draw let's say 15W from your 24V supply, I'd pick a unit rated for (at least) 30W and it'll likely run fairly cool. Again, thermally decoupling the power supply from the tempature-critical part of your system is the obvious main thing to do.
Yes, probably, but it would not be my choice; see above.
Thank you @rsmls@jremington , I'm going to go with 24V and buck down to 12v for the arduino using one of these regulators! It totally makes sense to me that your efficiency will be higher if you are doing the voltage conversion for the component which uses less power.
