Effects of Recirculating BEMF to Coil

[poynt99]

Hey MH.

I don't have to worry about slow connections, not since about 12 years ago But yeah I remember playing that game too. 

Glad those days are gone 

.99

[gotoluc]

Luc.

You can try the 1 Ohm.

The wave forms you saw are correct.

You have a pretty good meter there and it would be nice to use it. So this is what I would like you to do, if you are so inclined: We need to see how your meter interprets certain wave forms.

Does your signal generator have an "offset" function? What frequency are you using from your 555?

What I want to know about your meter is if we give it the following, what will it read out?

Generator  (1kHz)                   | Meter DC-RMS   |  Meter AC-RMS
________________________________________________________
50% duty, 0V-1V (pulsed-DC)
25% duty, ""
50% duty, -0.5V-+0.5V           
25% duty, ""

Hopefully one of the two (AC or DC) readings will be correct (I'll crunch the values), and then we'll know which to use across the 1 Ohm current sensing resistor.

.99

Okay .99,

since you have the manual to my meter you know more then I about it.

My SG is a Wavetek 134 and I don't think it has an offset but what do I know

The frequency I used on my 555 for the last test was 145Hz

That is about all I have.

Luc

[poynt99]

Hi Luc.

I found the manual for your 134 Generator here:
http://www.el.bqto.unexpo.edu.ve/tperez/LabME/MWavetek.pdf

It looks like it does have a DC offset control (+/-5V), but it is adjusted from the back of the unit

This is a pretty good generator too. You did well if you got it for $25

145 Hz? OK, I thought it might be quite a bit higher.

.99

[poynt99]

Luc,

There is also this if you recall I posted at EF a while back. This is simple and still valid for your recent testing. No special meters required if you do it this way.

Luc,

Here's a simple circuit suggested by aethertech and similar concept by gyula to ease input power measurements.

I had never tried this before so I PSpiced it up to check against the more direct method.

I'm happy to report that it seems to work quite well. All you need is a couple fairly large electrolytic capacitors and a sufficient wattage 10 Ohm resistor (or close). Connect as shown in the diagram here. If you use a wire-wound 10 Ohm it will filter even a little more.

Take two cheap DC voltage meters (both set on "DC Voltage"), one across R3 to measure the voltage across/current through it (I=V/R), and one across the Vbat point on the diagram to measure output voltage V.

Input power to the circuit is now Pi = V x I

Hope that helps.

.99

[gotoluc]

Hi .99,

I now see the DC offset ... what to do with it is another story

Hey, you even know I paid $25. for the Wavetek

Is there anything you don't know

Yes, you're right! I didn't try the capacitor resistor arrangement yet. I'll put it together and test it.

I'll post what I find or a video if it gets good score.

Luc