Digital Analog Trainers.

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Berticus81

Joined Aug 4, 2022
3
Hello everybody,

This will be my first post on this forum.
I am an electronics student approaching the finish of my A.S. Degree.
Id love to hear from anyone who has experience with the trainers.
I have an Elenco XK-700 to do my labs on at home.
I know what it does and the features it has. I have seen a couple decent videos.
What I am trying to do is use the 15vac for my source and run it through one of the pots to give me 6vac to the breadboard.
I could not get this to work on my old trainer. My teacher and I confirmed that the 1K pot was not functioning. Going through the 100K pot I was getting something. But not 6vac. I put my scope on the line coming from the 15vac source and I saw a very jagged ugly wave that kind of resembled a sine wave, but man it was not clean.
My question is: Is there any reason this method would not work? I’m pretty sure my old trainer was broken. I bought it used.
I just want to make sure I am not going to blow out the pots somehow with the regulated voltage from the source. I would think if the voltage source got shorted then the fuse would blow. Idk. Or maybe if anyone knows a lot about the Elenco and had some tips to share.
Thank you.
 

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MrChips

Joined Oct 2, 2009
30,815
Welcome to AAC!

You are asking about two different issues.

1) If there is a problem with the Elenco XK-700 Trainer I am sure that there is a good chance that we can get it working again.

2) You want to get 6VAC from a 12VAC source. Using a potentiometer is not the right way to do this. You will very likely burn out the potentiometer. This is a perfect example to learn how to apply Ohm's Law. What you need to know firstly is how much power do you need to supply at 6VAC. Without this information we are not yet out the starting gate.
 

crutschow

Joined Mar 14, 2008
34,454
One very important thing when using a potentiometer is to determine its equivalent output resistance and the power this will dissipate for the desired output current and voltage.
From this you will see why you don't normally use a pot to provide any significant output current.

Here's a good place to use the Thevenin equivalent circuit, which I assume you learned getting you A.S. degree, and how to determine it's values from the pot wiper position and element resistance.
 

dl324

Joined Mar 30, 2015
16,925
Welcome to AAC!
What I am trying to do is use the 15vac for my source and run it through one of the pots to give me 6vac to the breadboard.
I could not get this to work on my old trainer. My teacher and I confirmed that the 1K pot was not functioning. Going through the 100K pot I was getting something. But not 6vac.
Your teacher should have told you that using a pot is not the way to get 6VAC from your 15VAC source; unless the current required is low.
 
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