ebay board kits v 542 boards

[crossleymarko]

so hows this psu.... 48v 12a,,

http://www.ebay.co.uk/itm/600W-PSU-4...e#ht_500wt_715

[Jonathan]

That's good, but not the cheapest.

http://www.rapidonline.com/Electrica...-0-35v-88-3839

(They come up cheaper on eBay quite regularly.)

With capacitors and bridge rectifier (£5 max) will be just as good if not better. You can find the circuit on google easily...

[crossleymarko]

That's good, but not the cheapest.

http://www.rapidonline.com/Electrica...-0-35v-88-3839

(They come up cheaper on eBay quite regularly.)



With capacitors and bridge rectifier (£5 max) will be just as good if not better. You can find the circuit on google easily...

sorry im confused, you said a transformer around 50v, the one in the link is 0-35v.. what cap and bridge rectifier would i need...

also is there a thread or diagram i could use...

[Jonathan]

sorry im confused, you said a transformer around 50v, the one in the link is 0-35v.. what cap and bridge rectifier would i need...

also is there a thread or diagram i could use...

Due to the capacitors the open circuit voltage will be the peak voltage, not the RMS voltage of the sinusoidal waveform from the transformer. To (approximately) find the ouput voltage you therefore multiply by the square root of 2 and subtract about 1.2V for the diode forward voltage, hence 35*2^0.5-1.2=48.3V.

Bride rectifier:
http://www.rapidonline.com/Electroni...ctifiers-66254

Capacitor (3 or 4 in parallel):
http://www.rapidonline.com/Electroni...acitor-11-2993

The transformer has two 120V primary windings, so you connect them in series to get 240V then connect that to the mains via a fuse. There are two secondaries and you want the rated voltage, so put them in parallel to keep 35V but get twice the current and connect those two wires to the AC terminals of the bridge rectifier (marked '~'). The output waveform will now look similar to a loch-ness monster, so connect all the capacitors in parallel with the + and - terminals of the rectifier and double check the polarity is correct (if not they literally go bang).
If you're not sure then read up on it or just get the PSU on eBay.