how to attach wiring to this step down transformer to create a DC power supply

Thread Starter

nisha p

Joined Dec 26, 2017
20
attached is the picture of transformer I have.I also have a 3 pin plug point which I intend to attach to the given transformer .i don't where to solder the wiring.230V is to be stepped down.The transformer is 14-0-14 center tap transformer. someone, please do guide me in attaching wire for using ittrans1.jpg
 

dl324

Joined Mar 30, 2015
12,783
The side with three terminals is the secondary. Primary voltage isn't labeled, make sure it's rated for your line voltage.
 

Alec_t

Joined Sep 17, 2013
11,997
The winding having the thinnest wire and highest resistance will be the primary (mains input). Check for continuity with a multimeter.
 

-live wire-

Joined Dec 22, 2017
912
The datasheet would be really helpful, if you can find it. Anyways, just get rated schottky diodes and some capacitors to convert it to DC. Make sure to use a full bridge rectifier. Anyways, in terms of the wiring, DO NOT CONFUSE SECONDARY AND PRIMARY. This will result in 240/14 ~ 17x the voltage. More info would be helpful.
 

MrChips

Joined Oct 2, 2009
23,204
If you are building a AC to DC power supply, don't forget to install a fuse and on/off switch on the AC LINE input.
The fuse comes first followed by the switch on the same side of AC LINE input, never on the AC NEUTRAL.

AC LINE ---- FUSE ----- SWITCH ------ Transformer Primary
AC NEUTRAL ------------------------------- Transformer Primary
 

neonstrobe

Joined May 15, 2009
132
Check if you need 14V rectified (approx 20V unloaded) or 28V (rectified will be about 40V unloaded). If you use two diodes as be80be you will get your 20V supply. A bridge rectifier is more efficient in most cases but works best with a single coil, as the wire can be thicker on the secondary than if having to make room for two windings, but is also used on split secondaries for dual supplies (e.g. +/- 20V).

Check the primary voltage as you have been advised already. If you don't know what it is, can you find a low voltage AC supply (from another transformer) - preferably lower than 14V e.g. 6V but 12 maybe OK - connect this to the secondary and measure the output voltage on the primary (take care- this will be 110 or 220V if you apply approx 12V to the secondary).
 

Thread Starter

nisha p

Joined Dec 26, 2017
20
tran with groud.jpgI have connected primary and secondary .the primary portion using a scavenged power supply plug.Is there a way to connect ground pin to the transformer?and do help me as to where to connect the fuse.I want to build a unregulated 14 V DC power supply.Thank you for helping
 

ElectricSpidey

Joined Dec 2, 2017
1,563
You can connect the ground to the case using a lug terminal when you mount the transformer, using screws.

And the fuse belongs on the hot leg of the primary, before any other things like a switch, which should also be on the hot.
 

Thread Starter

nisha p

Joined Dec 26, 2017
20
You can connect the ground to the case using a lug terminal when you mount the transformer, using screws.

And the fuse belongs on the hot leg of the primary, before any other things like a switch, which should also be on the hot.
Could you please elaborate.I didn't understand.Thankyou
 

Dodgydave

Joined Jun 22, 2012
9,935
View attachment 143718I have connected primary and secondary .the primary portion using a scavenged power supply plug.Is there a way to connect ground pin to the transformer?and do help me as to where to connect the fuse.I want to build a unregulated 14 V DC power supply.Thank you for helping
Connect the Earth wire to the transformer case, scrape the paint/varnish from the holes on the fastening plate, and use an eye crimp or wrap the wire around the screw/bolt between two washers,. The fuse goes on the Live mains feed and ideally one on the secondary side rated for the load.
 

Alec_t

Joined Sep 17, 2013
11,997
The length is immaterial if it interconnects the left and right end tags of the transformer. Why is the red wire present and what does it connect to?
 
Is the three prong male plug (shown at the top of your photo) connected to the three hole socket--that is, are they going to be your power cord? If so, you can cut the cord and solder the outer wires to your transformer and the center as explained by other posts.

If the transformer is really 14-0-14 you will get more than 14 volts dc when you rectify the ac--nearly 20 under low load. Do you have a rectifier circuit in mind?

Most people fuse the hot side of the primary circuit. Some fuse the + side of the dc. Some even fuse both.
 
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