Who wants to know why more about DC Electronics? Ohms law part 1 and part 2

[k0ua]

OK, so anyone lurking out there learn anything? If so, do you think it will do you any good in the future?

 

[lilranch2001]

It did help me recall what I learned in my High School electrical classes James, I have used it in my industrial job for 15 years till I took over management of the plants I became responsible for.

 

[CalG]

If you are doing any electrical work on your tractor, get a VOM Volt Ohm Meter. Good ones are as cheap as $17!

It does not matter if the VOM is digital or analog! ! ! Learn how it works! Measure the voltage of dead batteries, measure the resistance of a light bulb. Measure the resistance of the two leads across your tongue!

LEARN HOW THE FREAKING THING WORKS. and what is reasonable. Learn that AMPS will blow the fuse, Learn that infinite resistance is likely a poor probe contact or a bad connection, not a broken wire. Learn that measuring Ohms means applying a voltage to what ever you are measuring, and 9V just might fry a 5V maximum component. Learn the E= IR and that if a component is not working, one of those three elements will be out of whack! Learn that GROUNDS and return paths are every bit as important as signal and source voltages. Learn that if a side clearance lamp goes on when the flashers are actuated you have a BAD CONNECTION TO GROUND.

Learn that electric motors, like fuel lift pumps and starter motors, have armatures with segments, and depending on position, one can read values at one instance that differ from the values taken later.

Learn that DC systems are easier to diagnose than A/C systems, but they are still hard!

Learn to set your VOM CORRECTLY! AC is NOT DC, Ohms are NOT Volts, Volts are NOT Amps, And Mega Ohms are NOT milli Ohms.

Cut out some resistors from an some random circuit board, and measure them. then measure them again!
Learn that a resistor in a circuit will NOT Measure it's labled value. BBROYGBVGW.

Learn that the Beep function of a VOM is not the same as measuring resistance. 2 Ohms can be a lot!
learn that 12.8 Volts is NOT the same as 11.2 V

Learn to play around if you want to be ready to play seriously.

And for the safety police, I^2R is HEAT! Don't start fires, you might get burned!

 

[CobyRupert]

Ohms do not keep Amps from rising up and ..... Ohms cause the restriction of the electron flow and create heat... Ohms are bad for current flow .... Bad Ohms... Bad, just Bad ..... [ I had all my electrical training back when they taught that the holes go from positive to negative, and the electrons flow from negative to positive, Columbus discovered America, they put the phrase ' under God ' into the pledge of allegiance, etc... LONG ago ]

Ohms do determine amps.
Ohms are what they are. They're the essence. The "it is what it is". It's not dependent on the others. You can't change the (DC) ohm's of "something" without altering what that thing is.

It's not like Ohm's Law works in all directions.

That is, Ohm's Law says you can make this 10 ohm resistor (10 volts across it and 1 amp through it) into a 20 ohm resistor if you give it 20 volts with 1 amp through. But that's not reality.

 

[MarkF48]

Everything I learned about electricity and other similar stuff was from this Youtube channel!!!!

ElectroBOOM

 

[mbohuntr]

Here's a little troubleshooting tip. If your DC system is acting screwy, such as trailer lights not blinking, or having voltage, but not lighting, LOOK FOR THE GROUND CONNECTION!!! If the ground is broken, lights won't turn on, if the ground is weak, blinkers won't work... Lift the ground off the frame, grind a clean spot, put some conductive electrical grease on it, and re-attach the ground.

It is probably the most found fault in troubleshooting. (at least for me it has)

 

[Industrial Toys]

I ws working on a DC motor drive last week on a machine that makes Tyvek suits. I thought the SCRS were bad, but they turned out to be OK. The transistor that fires them turned out to be bad. The transistor had been replaced before, and there was no information on it. Digikey got 70000 hits when inputting the number.

Schematics not anywhere to be found on this popular make of drive.

Anyway, there were only two other types of transistors on the PCB. PNPs and NPS all being the same. I guessed, the driver for the SCRS was PNP since the SCRs required a positive trigger or gate signal. But it did not work. Contacted someone on EBAY selling the same motor control and he was nice enough to provide the number of the OEM transistor. It was NPN! Put a generic one in, tht has been in my basement for thirty years and the thing worked.

I can't figure out why it was an NPN transistor.

 

[MossRoad]

OK, so anyone lurking out there learn anything? If so, do you think it will do you any good in the future?

Yes, I learned there's a lot of funny people here. As for the future, of course! :laughing:

 

[k0ua]

Yes, I learned there's a lot of funny people here. As for the future, of course! :laughing:

Yeah it didn't quite evoke the conversation and follow up questions I anticipated when I posted it.

 

[MossRoad]

Yeah it didn't quite evoke the conversation and follow up questions I anticipated when I posted it.

No good deed goes unpunished... eh?