Quick way to identify transformers

Say you got a transformer from a old stereo amplifier and you only know it can output 12volts maximum after rectification. You can’t find any data sheets for it since it is a custom built transformer for that amp line. So when you want to reuse it for a project such as a power supply you need to know if it is in phase or not since there are more then one pair of secondary taps.

To do this I would advise to use a one to one transformer so you can be isolated from earth ground and don’t have to worry about blowing your equipment up. However not everyone has a one to one transformer laying around so here is a quick way. It’s kinda dirty but it works.
To see if the transformer is in phase or out of phase a dual channel oscilloscope is used. One channel is connected to the mains voltage input and the second channel is connect to the output mains. However if you were to do this with out any isolation you will blow something up such as the oscope. Reason being the earth ground isn’t 100% earth ground but it is tied to the neutral line from the fuse panel or circuit breaker panel.
The easiest way to get around this is to not use the earth ground on the oscope. I’ve seen people use kapton tape and wrap it around the earth ground pin but I wouldn’t advise it. Since modern oscopes use IEC power jacks all you need is a typical IEC cable that you don’t really care about and do some surgery to it.
Go to a home improvement store and buy a replacement plug. I would go ahead and get a three prong unit for the sake you don’t mix up the polarities of the AC line to your scope.
Just wire up the new plug but leave the earth ground disconnected and cut off from the circuit.

North America – All you need to worry about is single phase.US-Color-Code-for-Electrical-Wiring.jpg

Most of the EU – Once again I would look at the single phase.

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After making a custom semi isolation cable you can test and see what set of secondary tap wires are in phase. You’ll know they’re in phase when the sine waves match.

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When they’re out of phase they will not match and look something like this.

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Reason why we want a in phase shift is it would be in sync. A out phase shift would make the transformer work harder and cause break down thus damaging the transformer.

News 4/11

Nothing new really. Started to pack up since the family and I are moving soon. Hopefully we can find a place that has a garage or something for a man cave so I can freely work on my many projects.

I received a laptop the other day. It’s a Acer MS2394 ES1-512 series. It was my oldest step son’s then he gave it to his mother and she turned around and gave it to me. Sadly it runs Windows 8.1 and no way in heck I want to update it to Windows 10. Half tempted to toss in more memory and toss Linux on it. I’ll keep Windows 8.1 on it for now. Maybe if I can get use to it I’ll like it more.

A friend of mine gave me a old flatbed scanner. It’s a Microtek Scanmaker 4900. It even has the LightLid 35 adapter for scanning film. I tried it on my tinker system and sure enough every Microtek scanner is compatible but not the Scanmaker 4900. I tried it on the Windows box and the USB doesn’t like it. I think it might be the USB supply is straining on the computer itself since all 16 USB ports are populated. If I can get the scanner to work I can finally scan some stuff from my notes from project builds.

I’m thinking to build a website since WordPress takes too much for posting images. I have to upload the pictures to the computer then re-upload them to my WordPress account. For myself it would be easier to just upload them from the camera from running a script of some sort that will copy the pictures to my HTTPd server’s image gallery. With that said I can just do a HTML address link to the images/pictures here on WordPress.

I also need to find a cheap video camera. A family friend is getting married this month and she wants me to video record the wedding. If I can get a decent camera I can then use it for maybe some video footage for stuff I’m working on and also forward my knowledge to others.

Oscilloscope Octopus

This is part of a all-in-one unit I am building for my scope. After going through the different parts I plan to use I’ll soon enough will create a whole unit.

You can test components with a Oscilloscope the same way you would use a multi meter or a LCR meter. Instead of a numerical readout you use a Lissajous pattern.

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Function Generator

A function generator is usually a piece of electronic test equipment or software used to generate different types of electrical waveforms over a wide range of frequencies. Some of the most common waveforms produced by the function generator are the sine, square, triangular and sawtooth shapes.

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Power supply rebuild update

Since I got the scope I can finally see what I am doing with the power supply build. After thinking things over for the specs of the power supply I decided to just to go with 30volts and 1.5 amps. Since 90% of most modern electronics you only need 1amp at most so a LM317 with improved ripple rejection is enough to get things working.

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Finally got a scope

Last night I was “windows shopping” on Craig’s list and found a Elenco S-1330 25Mhz analog scope for sale for $60.00. So I emailed the guy and offered 50 and he accepted.

The scope is in great shape. No CRT burn in or anything.

When I got home with it I wanted to nap the photo from the listing but the guy already took it down. However Ebay is riddled with pictures.

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First thing I tried it out on was a cheapish function gen that my LCR meter has and I can get a 1000kHz square wave just fine. I then tested my second attempt of a power supply build and just as I thought I had no ripple on the output.

A scope is a great tool for any electronic testing. If you don’t have a scope I would suggest to get a analog scope. As long as you’re not doing too much with high speed digital circuity¬† a 25 to 100 MHz scope is plenty.