I keep a long string of series silicon diodes handy to experimentally drop motor voltages. Each diode drops a fixed ~0.7 volt, so with a few alligator clips you can step up or down 0.7 volt at a time. They do heat up like a resistor, but they are far superior at high loads when the motor is near stalled, because the resistor drops more voltage as more current flows, and the motor torque drops off.
You'll want BIG barrel diodes for the current you're pulling. Even the Shack has a pack.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ ·"If you build it, they will come."
@erco,
This is an excellent idea to use what most people would consider a defect in diodes to achieve a resistance drop without a resister.
A 10 amp diode is sure cheaper then a 10 watt resister!
Thanks for this tip!
P.S. I’m going to start a new thread in the sandbox on signal wire routing.
Gramps
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'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
Diodes are a guy's best friend! They allow a fixed VOLTAGE (not resistance) drop of 0.7 volts. Schottky diodes only drop 0.3 volt, handy for finer voltage drop adjustment.
A favorite trick of mine is to use 3 of them in series as a current sensor (two doesn't work reliably). If you just need to tell if an external circuit is on or off, insert the series diodes at the battery negative terminal. This assumes your circuit operates at ~6V or higher and won't miss 2 volts. Now attach ground wires between your circuit and stamp, and attach the anode end of the 3 series diodes to a stamp pin (a 220-ohm protection diode is wise). Now when your circuit has current flowing (headlights, battery charging, etc) your stamp pin reads high; and when no current flows, pin reads low.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ ·"If you build it, they will come."
Comments
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'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
You'll want BIG barrel diodes for the current you're pulling. Even the Shack has a pack.
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·"If you build it, they will come."
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
Is that a question, or a statement, or a lamentation, or a way of life?
6 amps: http://www.radioshack.com/product/index.jsp?productId=2062591
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·"If you build it, they will come."
I have some 1 amp.........
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·"If you build it, they will come."
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
Fewer diodes allows a higher stall current, obviously.
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·"If you build it, they will come."
This is an excellent idea to use what most people would consider a defect in diodes to achieve a resistance drop without a resister.
A 10 amp diode is sure cheaper then a 10 watt resister!
Thanks for this tip!
P.S. I’m going to start a new thread in the sandbox on signal wire routing.
Gramps
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'What is your life?"
"It is even a vapor that appears for a
little time and then vanishes away."
Saint James 61 A.D.
A favorite trick of mine is to use 3 of them in series as a current sensor (two doesn't work reliably). If you just need to tell if an external circuit is on or off, insert the series diodes at the battery negative terminal. This assumes your circuit operates at ~6V or higher and won't miss 2 volts. Now attach ground wires between your circuit and stamp, and attach the anode end of the 3 series diodes to a stamp pin (a 220-ohm protection diode is wise). Now when your circuit has current flowing (headlights, battery charging, etc) your stamp pin reads high; and when no current flows, pin reads low.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
·"If you build it, they will come."