1. I bought a couple ac wall warts for projects. I wanted 12v out and they actually put out 14.69vac. Keeping it simple, what can be done to reduce that output to the 12vac I want?
2. On a lark I checked my cw80 and at full throttle it only puts out 14.87vac. Manual sez 0-18 or 0-16. Am I just expecting too much from this transformer, or does load and other factors enter in to the measurement?
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Those cheap little wall warts are UN-regulated. This means they will show more than their rated voltage when they do not have any load on them. A volt meter is not a load.
As soon as you put even a small load on it (light bulb, etc.) they will show the rated voltage.
Thx for the help. I put some bulbs on and the voltage dropped as described. TW
Are you checking the CW80 with a load?
That needs a load for a good reading also. A lighted car or a bulb.
The Harbor Freight meter you're using won't measure non-linear waveforms accurately, you need a true-RMS meter for the CW-80 measurement. Here's what the CW-80 looks like at full throttle, is it any wonder that the meter is confused? It has some serious ringing at the switch points, also why it drives many MTH locomotives nuts.
gunrunnerjohn posted:The Harbor Freight meter you're using won't measure non-linear waveforms accurately, you need a true-RMS meter for the CW-80 measurement. Here's what the CW-80 looks like at full throttle, is it any wonder that the meter is confused? It has some serious ringing at the switch points, also why it drives many MTH locomotives nuts.
Hey, don't knock my precision instruments. 4 bucks with a coupon! The "ringing" I'm guessing, refers to the red arrow locations in my edit of your screen shot and not the yellow circles. What does this mean(if there is a short version)? Does this waveform fit the power/engine electronics requirements better, or is a xfrmr built like this cheaper? Why is it made that way if it's undesirable?
Yes, the ringing is the oscillation indicated by the red arrows. It's just when the triac switches on, the circuit oscillates and produces that high frequency burst of noise on the waveform. That should have been fixed in the design, but it's a cheap transformer and I guess they didn't think it would cause a problem. Notice the 'scope sees 24khz for the frequency of the ringing.
Aren't our scopes wonderful tools. They let us see things others can't.
Why would Lionel fix something that makes the competitions product go nuts?
gunrunnerjohn posted:Notice the 'scope sees 24khz for the frequency of the ringing.
Since you made note of this number, what is the significance?
choochoopaul posted:Why would Lionel fix something that makes the competitions product go nuts?
Very good point! 
TedW posted:gunrunnerjohn posted:Notice the 'scope sees 24khz for the frequency of the ringing.
Since you made note of this number, what is the significance?
No particular significance, the presence of the ringing waveform is the significant feature.
John,
Love the scope waveforms. I have a few scopes myself and they are invaluable for measuring what happens in time. I refer to them as time machines.
A Time Machine and a Shrink-a-Tron WOW!!!
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