HP ScanJet power supply as a power supply for amp

Jump to Latest
brskovacevic

brskovacevic

Member
Joined 2010
#1
Dear all,

After some time I am again in DIY area, so I have (perhaps stupid) question...
I have two sparate PSU from HP, I think from some printers or scanners. Model 0957-2260, output voltage is DC 32V and output current 5625 mA, what is OK for my application. Of course, I need two of them to have symetric power supply +32 -GND- - 32V.

Question is: is it possible to connect theirs outputs to achive desired voltage or not? It means that I have to connect plus from one to a minus of another one to have central point.

Something rings in my head that someone told me that I need to do something with input connection (230VAC), but cannot remember what was warning...

Any ideas, advices?

Thank you in advance, regards,

Boris
 
#2
It depends on the output being isolated from the input. If there is a transformer in the circuit you have a chance it will work. With it powered off measure with an ohm meter between the individual DC output connections, plus and minus, and each of the AC input connections. If it is many megOhms, you are good to go. If that looks good you could do a trial connection between the positive output of one with the negative output of the other using a resistor, maybe 10 kOhms. If when powered up there is no voltage drop on that resistor, AC or DC, you are looking good. If the product was only wireless and had no USB or wired network connections it is possible they could save a little money with a non-isolated power supply which would not work for you.
 
#4
@rayma Using two of them to achieve a bipolar power supply does not require flipping one around. You simply wire them in series, and use the center point of the two as your circuit ground reference. The potential across the two other terminals would then be the sum, and the potential across each one and the center point their respective output voltages.

As far as I know these power supplies are the type with a ground pin though, which likely means they are inherently not "double-isolated". For that, I'd follow the advice @olsond3 has provided.
 
#5
When connecting the supplies in series, the "negative" supply must have its positive output connected to common,
and its negative output floating and not grounded. This is what was meant by flipping its outputs.

But typically the negative supply terminal is connected to the circuit common, and is normally grounded to the chassis.
Possibly the supply could be rebuilt to float the negative terminal so it could be used as part of a dual supply.
 
You must log in or register to reply here.
Top Bottom