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Topic: 12VDC (0.35A) Motor with 1N4001 Diode? (Read 8440 times) previous topic - next topic

raschemmel

Quote
I think diode temperature is the thing you're looking for.
Most, if not all, diodes are fast enough to take the start of the back-EMF current.
Only the diodes that turn off faster are "ready" when the mosfet switches on again. 
I don't have apples to compare to apples or oranges to compare to oranges.
At the moment all I have is apples and oranges (1n4001, 1.5KE350A. 1n5711, & 1n5822)

I placed an order for 1N5818s but it's coming from China.
If I need something other than what I have now I will have to order it.

larryd

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raschemmel

Quote
Across the inductor.
That's a show stopper.

 Even with both my power supply and my scope both plugged into 3-prong to 2-prong
adaptors my power supply shuts down (goes into current limit shutdown mode) if the scope ground touches either Vcc (cathode)  or the drain (anode) of the diode and I don't have a DIFF PROBE.

I have no way to measure across the inductor without a diff probe.

larryd

#33
Dec 19, 2015, 06:24 am Last Edit: Dec 19, 2015, 06:24 am by LarryD
Even with the scope isolated from earth ground?
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raschemmel

#34
Dec 19, 2015, 06:29 am Last Edit: Dec 19, 2015, 06:36 am by raschemmel
Quote
Even with the scope isolated from earth ground?
YES.

The only chance I have of obtaining that measurement is if I make my own DIFF probe, because I sure as hell can't afford to buy one.

larryd

#35
Dec 19, 2015, 07:05 am Last Edit: Dec 19, 2015, 07:05 am by LarryD
Makes no sense to me why there is a connection to earth if the ground lead is gone.
Never seen that.

The scope isn't pushed against another grounded piece of test gear?

When you measure with a DVM what resistance do you see scope chassis GND to the AC plug pins.
(Things powered off obviously).
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larryd


 :o

Same with the other equipment I assume (ass u me ;) ).

Well, one option is to keep an eye out for a 1:1 isolation transformer to power the scope.

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Wawa

#38
Dec 19, 2015, 08:13 am Last Edit: Dec 19, 2015, 08:27 am by Wawa
AFAIK it's common for the scope to be grounded, and the supply to "float" (except for the metal case).
So you can combine supplies for double voltage, double current, or a bipolar supply (one with positive to ground).
Some lab supplies have a third ground terminal.
Leo..

larryd

#39
Dec 19, 2015, 08:26 am Last Edit: Dec 19, 2015, 08:31 am by LarryD
Quote
AFAIK it's common for the scope to be grounded,
Yes.
For protection.
Never defeat the earth lead or use an isolation transformer unless you are 100% sure you understand the ramifications of doing so.

You can use a scopes math function and two channels to do differential measurements.

Of course you can power your circuit with a battery (or isolated supply) not having any part of the device referenced to earth.
You can then reference anywhere.
.
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TomGeorge

Hi,
I assume your CRO is  single channel?

Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

raschemmel

#41
Dec 19, 2015, 05:07 pm Last Edit: Dec 19, 2015, 05:16 pm by raschemmel
Quote
I assume your CRO is  single channel?
  
Look again



FYI,
I have some LT1215s and I  have already used them for Differential Amplifiers in other posts so that's no problem but I don't yet know how to combine them opto isolators to make an isolated DIFF AMP,
not that it is necessary.

Note: Look at the red price tag... :D

yendis

If your scope has 'invert' on one channel, and 'add channels' mode your display will read differentially.
Chris

TomGeorge

Hi,

Quote
If your scope has 'invert' on one channel, and 'add channels' mode your display will read differentially.
Exactly..

Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

raschemmel

which channel goes where and which one gets inverted ?

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