Electronics > Beginners
Why does the "dim bulb test" limit current instead of adding load to the supply?
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ebastler:

--- Quote from: Beamin on August 19, 2018, 04:30:38 am ---I know I have asked this before but what are good examples of beginner versions of the spice program? There was one where you would see red and green lines that show current flowing through them. Are there any that you can download rather then web base?
[...]
Spice is too technical where it gives you the box with numbers in it, very useful if you are doing complicated stuff but I need something in between that and the web based tool. One where you could simulate poking a scope probe around or DMM.

--- End quote ---

Give TINA-TI a try -- free download at http://www.ti.com/tool/TINA-TI. It is a pretty friendly Spice front-end. A simple schematics editor, and while it does not color-code the wires to show current flow as you describe, it lets you connect virtual voltmeter probes and a virtual oscilloscope to the circuit.
Seekonk:
I used a lamp as a constant voltage source! We had a low voltage detection board.  Production needed a cheap tester for it and the board had to trip at the same value of mv AC as DC.  I used a small lamp in a bridge circuit and either switched AC or DC into the bridge.  Line voltages of +- 20% did not phase it, spot on within 1mv. Though it doesn't respond quickly to line changes. All the tech needed to do was to cal the test box on DC with a cheap meter. Switching to AC would be the same mv RMS as the set DC value.

I first learned about the dim bulb test in about '64.  EICO had an ad for an amplifier kit. It pictured a lamp next to the kit and said the only piece of test equipment needed was a lamp.
Beamin:

--- Quote from: Seekonk on August 19, 2018, 11:13:51 am ---I used a lamp as a constant voltage source! We had a low voltage detection board.  Production needed a cheap tester for it and the board had to trip at the same value of mv AC as DC.  I used a small lamp in a bridge circuit and either switched AC or DC into the bridge.  Line voltages of +- 20% did not phase it, spot on within 1mv. Though it doesn't respond quickly to line changes. All the tech needed to do was to cal the test box on DC with a cheap meter. Switching to AC would be the same mv RMS as the set DC value.

I first learned about the dim bulb test in about '64.  EICO had an ad for an amplifier kit. It pictured a lamp next to the kit and said the only piece of test equipment needed was a lamp.

--- End quote ---


How did that work? Put the bulb in series with it and as the voltage changed the resistance of the bulb would change? Less voltage cooler filament and it would go down in ohms? Or am I mixing up current with voltage? My ignorance of E=IR reminds me of a louis rossman video where he says he never learned BlkBrROYGBV out of spite for a teacher he had. That's a brilliant idea to paint rainbow colors on a beige or blue back ground
SG-1:
Ohm's law states that the electrical current (I) in a closed circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). When the voltage is increased, the current will increase provided the resistance of the circuit does not change.

Most versions of ohms law, especially the simplified math version leave out two critical statements that allows one to know if the formula application is valid. Those two statements are in bold text above. If the measured value does not match the calculated value those statements can provide clues as to why the desired results were not achieved.
Beamin:

--- Quote from: SG-1 on August 19, 2018, 11:39:08 am ---Ohm's law states that the electrical current (I) in a closed circuit is proportional to the voltage (V) and inversely proportional to the resistance (R). When the voltage is increased, the current will increase provided the resistance of the circuit does not change.

Most versions of ohms law, especially the simplified math version leave out two critical statements that allows one to know if the formula application is valid. Those two statements are in bold text above. If the measured value does not match the calculated value those statements can provide clues as to why the desired results were not achieved.

--- End quote ---


After reading that it all comes back to me. Its frustrating it's like I know I know something but can't quite reach it. This hobby is use it or lose it or at least with me the math is. Not to long ago a friend's son  was over my house and he saw math problems out on my table. He asked if I was in school I said" no I had to figure something out( building an antennaat a different wave length)I was board" and he said "you mean you do math when you don't have to?" Yes math makes life easier.
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