Hello fellow builders! I just started to build some cooling for my electronics. I have a power supply 230VAC 18A that gives 24VDC I found one shematic that allows me to drop the voltage from 24VDC to 12VDC using resistors in series. I used two 10K ohm resistors in series as shown in the picture. I connected resistors and measured my output voltage without connecting the ventilator, and it shows 12VDC as it should be. The problem is, once i connect my ventilator to the output wires, it wont turn and the output voltage drops to 2,2 VDC. I have another small power supply that outputs 12VDC and i tested the ventilator with it. so ventilator should spin. Is there something that im missing? Is there a way to fix it somehow? Sorry for the bad drawing Thanks!
If your ventilator draws a current of 0.25A then it's resistance is 48 ohms. You have connected this resistance in parallel with the bottom 10K ohm resistor. I could do the math to work out the effective resistance of the bottom leg of your potential divider, but it's very close to 48 ohms. There are DC to DC convertors, but frankly the simplest solution would be to provide your ventilator with it's own 12 volt power supply. Check sites like Ebay and Amazon for plug in power supplies (like those used for laptops) - apart from getting the right voltage check the current rating and get one that can supply say 0.5 Amps. Alex.
You should use a buck converter transform the voltage. They can be found for a few dollars on eBay. If you need to use a resistor then you should make sure that your resistor can handle the 4W or so you’ll be putting through it. And as suggested, a 24v fan might be the cleanest way to go.
Thanks guys! I will indeed use a seperate power supply that can grant me 12VDC that i need. Every day learn something new
