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I'm working on a project which involves a DC heating element, a computer fan and an Arduino/ESP8266. I'd like to use one power supply for those devices.....

The requirements:

  1. The heater needs a steady 12V / 1A DC
  2. The fan needs 0 - 12V to operate
  3. The Arduino/ESP8266 needs 3.3 or 5 volts
  4. Here in Belgium, we have AC 220V mains electricity. I'd like to use 1 power supply (for instance of a laptop)

Here is a schema of the project:

I have 2 questions:

  1. How much Volts/Amps does my power supply need, to get those 3 things working, safely, without overheating?

  2. How do I connect the devices to the power source so that the Arduino/ESP8266 isn't getting to much volts/amps when the heater is switched off or the fan is shut completely down?

Looking forward to some suggestions!

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    \$\begingroup\$ THere are so many solutions you can buy with AC to 12V and variable DC-DC output that are >80% efficient. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Jul 22 '19 at 20:47
  • \$\begingroup\$ Measure the current of each device or find it in a datasheet. Then size the supply accordingly \$\endgroup\$ – Voltage Spike♦ Jul 22 '19 at 21:20
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Finding a laptop power supply that is dual secondary voltage might be hard. How about a small power supply from a desktop computer? They would have all the voltages you need and have great spike protection. I think a 50va, 50 watt power supply would be all you would need if you can get one that small. Good luck, have fun.

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  • \$\begingroup\$ Agreed, a power supply salvaged from a scrap PC will give you all you want. Try to find the more modern ATX one with a 24 pin connector. More information than you could ever need here and even more if you google "PC power supply". Maybe make a bench power supply like this \$\endgroup\$ – Peter Jennings Jul 22 '19 at 23:45
  • \$\begingroup\$ I have a spare power supply around, so I will give it a try. Do i connect the devices straight to the power supply? Do i have to worry about 'burning' one of the devices? I think my spare supply has 36 volts. \$\endgroup\$ – De Pauw Jul 23 '19 at 14:03
  • \$\begingroup\$ You need to look at the name plate on the ps and determine which wires give you the voltages your devices need. You mention 36 volts. Do you mean 36 watts?. I would use a male/female plug arrangement for connecting the devices to the ps. \$\endgroup\$ – JACK Jul 23 '19 at 14:23
  • \$\begingroup\$ sorry for the misunderstanding. I was thinking of a laptop power adaptor. But indeed, your solution, a real pc power supply will do the trick! Thanks! \$\endgroup\$ – De Pauw Jul 24 '19 at 8:19

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