Converting 240v To 20V DC

[ScottishGasMan]

Hey all. Will explain this one a little first.

I have a hot water circulation pump, powered by a 240v AC feed, max about 25watts. I'd like to use it on my own hot water cylinder, but it also has 2 wires to feed a DC signal to it. The DC signal I belive is 22V to start the pump settling at 17v normal operation but will modulate up and down to suit heat requirement.

I dont need it to modulate, I just need it to start and run using the 240v feed that will turn on and off as required.

So my question is what is the smallest bit of electronics I can get to convert 240 to 20vDC, doesnt need to handle load as its just a switching signal. Ideally I'd like to house it in the pumps electronics but its pretty tight in there so If its has to be a transformer then Ill need to make up a box to house it.

 

[bernardgreen]

Quickest solution would be a laptop power supply as they are typically 19 volts but may be a bit on the big side.

 

[JohnW2]

Quickest solution would be a laptop power supply as they are typically 19 volts but may be a bit on the big side.

Indeed. In fact, if one searches, there are any number of 'power adaptors' which provide ~20V DC output (often as an option in a multi-voltage one) - but, again, fairly big (and often 'wallwarts'). The only 'small' approaches would probably be simple component-based ones - but, if the OP does not already have the knowledge to do that, it's probably not the approach for him.

Kind Regards, John

 

[bernardgreen]

Have a look around this site

http://www.tracopower.com/home/

A lot of Traco modules can be bought from RS Components