Effects of Recirculating BEMF to Coil

[gotoluc]

Thanks .99 for your post and offer to help as always

My batteries are not fully charged as I have not re-charged them since I started the series of battery tests.

I do have a shunt but I think it's too large for my delicate tests,  it's stamped 60A 75mv and FL - 2 (unreadable symbol) 0.5

I tried it with my probe across it on the negative feed side and see no peaks during the on time. However I do have a one watt carbon 1 Ohm (brown, black, gold, gold) resistor that I tried and it shows the on peaks very well.
The duty cycle is much lower when connected straight to the resistor then to the coil and the wave form on the scope is very different in each case. Strait to resistor is much like the on pulses of the 555 but with slightly rounded corners and connected to the coil it goes up on a 45 degree angle and drops straight down when switched off.

I don't trust the RMS reading my scope calculates since it changes quite drastically when increase the times division. So I'm lost as how to calculate it.

Luc

[poynt99]

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

[MileHigh]

Luc and .99:

That's a really great multimeter.  I was doing some hunting and you might find this  interesting:

The Schlumberger / Solartron 7150, 6.5 Digit Benchtop Multimeter features AC & DC voltage ranges 0.2 V to 1000 V (5 ranges, true RMS on AC). Resistance ranges 2 kohm to 20 Mohm (5 ranges). Linearity < 0.001% of range. DC current to 2 A, ac current to 2 A. Temperature measurement mode (-200 C to +600 C, requires additional platinum resistance probes).

http://www.teknetelectronics.com/DataSheet/SOLARTRON/SOLAR_7150103803.pdf

MileHigh

P.S.:

I found the Mother Load, but it is a really slow connection, best to "save as."

[EDIT:  The link below gives you access to the 7150 Plus user manual.  Click on "7150" at the botttom of the page.]

http://bama.sbc.edu/solartron.htm

[poynt99]

Hey MH.

Yeah,

I've had the manual downloaded some time ago shortly after Luc first showed it on his videos.

.99

[MileHigh]

Smart ass. 

P.S.:  Did you ever notice how you have to use "mind power" to keep a download with a slow and flaky connection going?  I swear, if you take your eyes off of it for too long it stops.  Then a good "mind power" stare-down session gets it going again.  Do you think we can tap into that?  lol

P.P.S.: It's not me it's them.  I have a vanilla DSL connection.  In my case very occasionally I come across a site that has a good server and nobody around.  I downloaded a game demo once from an Australian web site at a nice blazing 600K.  That distinctive modem negotiation sound is now a distant memory.