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Topic: monster-in-a-box setup HELP (Read 119 times) previous topic - next topic

heropants

I apologize if this is a noob question, I'm really just starting to get the hang of things like transistors. I'm trying to control a 12 volt car door actuator (will make a lid pop up). I believe when the actuator is powered, it pops up and when unpowered, it drops back down. Since the actuator requires 12 volts, I figured I could use the same setup that people use for powering a 12 volt motor (using a transistor).

I'm wonder if anyone could tell me if this setup looks correct. I wanted to mention that the resistor between the Arduino and the transistor will be 1k, not 220. Also, I understand what diodes do, but have no idea why I need a diode where it is on the image. The transistor is an NPN transistor but I have no idea what exact type I'll need beyond that.

Thank you so much in Advance!


groundFungus

#1
Feb 13, 2018, 05:12 pm Last Edit: Feb 13, 2018, 05:19 pm by groundFungus
The diode is to protect the transistor from the high reverse voltage that occurs when the motor is turned off and the magnetic fields in the motor collapse. 

The power supply needed depends on the current requirements of the motor and its rated voltage.

To choose a transistor to control that motor, the motor stall current must be known.  I would use a logic level MOSFET, here.

A 220 Ohm resistor is fine.  It will still keep the base/gate current less than 20mA (the safe current from a pin) and insure that the transistor is saturated.  If using a MOSFET, a pull down resistor (10K), in addition to the gate resistor, will keep the MOSFET turned off if the controlling pin is hi-z (during reset till the pin is set to OUTPUT).

heropants

Okay, thank you! I'm guessing that my set-up here is correct then (no obvious errors in the way I've got the wires, besides the pull-down resistor). I'll use a MOSFET transistor then. Thank you!

wvmarle

Better post a proper circuit diagram, those Fritzy images are worthless when it comes to checking circuits. Even a rough hand-drawn sketch is a lot better than that.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

heropants

Better post a proper circuit diagram, those Fritzy images are worthless when it comes to checking circuits. Even a rough hand-drawn sketch is a lot better than that.
Sorry, I'm just getting into this and I have a much better grasp on where I plug wires into then I do on how schematics are suppose to be drawn. Just out of curiosity, for a beginner, aren't the fritzy images more helpful because they show exactly how the circuit is going to be constructed? Like if you show me a schematic diagram with a bunch of symbols and lines, I don't think I could create that on a bread board. But if you show me a fritzy image of the breadboard, it's pretty easy to see exactly where I need to plug things in.

wvmarle

Sure, it can help you figuring out how to wire things, but you can't make a proper wiring diagram without knowing how your components link together, for which you need to know how to draw a circuit diagram.

Without knowing how your circuit should be, how can you ever get the wiring right?

Point in case: that MOSFET. Which type? What's it's pinout? How can you be sure it's wired correctly? Wrong wiring can easily destroy the part.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

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