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Topic: battery current to the plate (Read 1 time) previous topic - next topic


the yellow wire should be in that position? If the yellow wire is in position, current will flow from the battery to the Arduino via the GND, then. You can break the plate?


what is it? you might get more help if you provided a few basic details, eg: part numbers.



For driving a DC motor in one direction only the relay-driving circuit will do.  The diode is not optional.
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Not really sure what your question is, but your layout is essentially the same as this.
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Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0


Transistors don't have a "plate". That is terminology from the old Heat Emitting Transistor )(otherwise known as a vacuum tube...).

Depending on the transister, but we generally use and NPN on the low side meaning the motor is between the positive terminal of the battery the collector of the transistor and the emitter is tied to ground. When a voltage (above .7 VDC, again depends on the transustor) is applied to the base the transistor turns on.

Arduino ground needs to be tied to the Battery negative terminal. The resistor between the transistor and the Arduino is optional as you are using the transistor as a switch and not as an amplifier. Might want to put a resistor from emitter to ground to make sure the transistor turns off all the way.(bleeds off any leakage from the output pin)


I = current flowing out of the stack.

I1 + I2 = I

I2 is current going to the Arduino. Is it dangerous to this current (I2) go to the Arduino?


If you don't provide us with a specific part number for the transistor/FET/vaccuum tube we can only guess if your wiring is correct.
Is it dangerous to this current (I2) go to the Arduino
Depends on the current limiting resistor between pin2 (arduino) and base (transistor)



I am concerned to know the values ??of:

1) Resistance (For I prevent the passage of current through the base => arduino)

2) The passage of current I2 to the plate.

I do not know if these values ??are obtained from the data sheet

(Thank you very much for all the responses.)


Dec 28, 2012, 08:05 pm Last Edit: Dec 28, 2012, 08:12 pm by retrolefty Reason: 1
I = current flowing out of the stack battery.

I1 + I2 = I

I1 current is just that from the battery through the motor, through the collector/emitter and back to the battery. I1 does not flow through the arduino board.
I2 current is just that from the arduino output pin through the base resistor onto the base emitter and back to arduino ground. This current is from whatever voltage source is powering the arduino board.

So there is no I (total) = I1 + I2 as they are separate current flows from separate voltage sources.
The only place there is a I (total) = I1 + I2 is at the emitter terminal of the transistor.

I2 is current going to the Arduino. Is it dangerous to this current (I2) go to the Arduino?

I2 is only the current flow allowed by the base resistor wired to the transistor's base and returning to the common ground of both the battery and the arduino.



Dec 28, 2012, 08:27 pm Last Edit: Dec 28, 2012, 08:38 pm by seanz2003 Reason: 1
1) Resistance (For I prevent the passage of current through the base => arduino)
usually 1k-220 ohms is acceptable, But it really should be calculated using the datasheet.
2) The passage of current I2 to the plate.
Depends on the motor windings resistance and the load on the motor (no load<<loaded<<<stall). This information should also be found in the datasheet. You could possibly use a ammeter to measure this and then select a transistor with 2x or 3x the maximum rated current. But the datasheet is usually the safest way to go. I2, as you have labeled it, is the same current that flows through the current limiting resistor, so you just select  the proper value for that resistor to limit the return current through ground. **sorry I read the question wrong**


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