[serkanozfe]

hi
i have started to build hobbycnc. my main board is done, and now i am going to build power supply. i bought 115vac - 24vac 1a Transformator, it has 5 cable, i put pictures about that.
and i checked alot but i couldn`t find part specification for power supply actually i found some things but they aren`t enough for me.
so i have some questions.
did anyone use 115vac - 24vac 1a Transformator ? and how to pick capasitor and bridge rectifier for this kind of transformator ? does anyone know what is the specification for capasitor and rectifier ? and how to connections for 5 cable.
Thanks...

[cjmerlincnc]

Hi, Looking at the pics, On the transformer it looks like your 2 black wires are the 115v and the 3 wires are what's called a center tap configuration. You will have to measure the voltage at the 2 green wires, If it is 24v then you can ignore the middle wire (green/yell)
if the voltage is larger then you can use only one side of the winding for 24v (eg: one green and the green/yell) wire.

The bridge rectifier needed will have to handle the 10 amps plus a bit more. Pick one that is say, rated at 50-100v 15-20A.

You capacitor will need to be at least 10,000uF and 40-50V.

Hope this helps.

[bbj]

hi
i bought 115vac - 24vac 1a Transformator, it has 5 cable, i put pictures about that.

I hope you left out the 0 (zero) on the transformer rating. 1A aint gonna get you very far. You need 10A.

[James Marshall]

Do not use that transformer or any other unless you are sure that it is NOT a auto-transformer. You need a isolation transformer or you will fry something. Trust me I did it!!!! I would suggest to buy or pick up some used ATX computer power supplies. Get three of them and look up the thread or google "How to turn a ATX power supply into a bench power supply". Make sure that you isolate the ground plane on the curcuit boards on all three, not just one, in the power supplies and use three of them to make 36VDC. This works good for my Hobby CNC pro 4 axis board.

[serkanozfe]

thanks for answers . i made a mistake it`s already 10a.
and i have seen at the hobby cnc home page that i need 24VAC 10A Triad (Magnetek) Allied Electronics part #9678482 (115VAC Only).
http://www.hobbycnc.com/hcncpropkg.php
so i bought same transformator from same company...
James Marshall , are you sure i can`t use this transformator, because i dont have any idea about electronic and this power supply. so i wanna make sure everything are correct.
thanks

[serkanozfe]

i found some thing about "How to turn a ATX power supply into a bench power supply"
http://www.youtube.com/watch?v=FFNEJBK3EsM

http://www.wikihow.com/Convert-a-Com...b-Power-Supply

but i need min 24v 10a...

[neilw20]

thanks for answers . i made a mistake it`s already 10a.
and i have seen at the hobby cnc home page that i need 24VAC 10A Triad (Magnetek) Allied Electronics part #9678482 (115VAC Only).
http://www.hobbycnc.com/hcncpropkg.php
so i bought same transformator from same company...
James Marshall , are you sure i can`t use this transformator, because i dont have any idea about electronic and this power supply. so i wanna make sure everything are correct.
thanks

Measure ohms with a multimeter between one of the black wires and one of the secondary.
If you get infinite reading (open circuit) then it is not an AUTOTRANSFORMER.
By the label it looks OK. Test to be sure.

[Greolt]

Serkanozfe

Don't get scared off. Do what Niel said above. Then refer to post number 2.

That should be a perfect transformer with which to build your power supply.

Greg

PS: for a good explanation of linear power supply go to this link, http://www.campbelldesigns.com/how-t...wer-supply.php

[rippersoft]

In both schematic diagrams, a resistor is shown across the terminals of the capacitor. If this is a bleed resistor, then a normally open (NO) switch should be added so that the resistor bleeds when you want it to. otherwise that resistor will get very hot and smoke something.

Your approach to building a powersupply for the HobbyCNC board is a good one. I built my first PS from basic parts, transformer, rectifiers, capacitors, terminals, etc and it still runs like a top.

Your 24VAC transformer after the capacitor should yield 34VDC +/- a volt or 2 depending on age of the transformer.

RipperSoftware

[Greolt]

Just use a 1k 5watt resistor. It'll be fine.

[serkanozfe]

Thanks alot. these are going to help me alot. let me try some thing then i`ll write what`s going on here. thanks again.

[Degrom]

Hi. Looked at you power supply circuit and I was just wondering about the fuse on the DC side of the circuit.

Why is the fuse just after the transformer and not before the out put terminal?

I would have thought you would want to protect the output more than the rectifier or the capacitor ( cause they are rated to withstand extra power...)

Just my thoughts,what do you guys think?