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Author Topic: several quiestions controlling dc motor [together with controlling light]  (Read 1138 times)
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ok. because come across several little problems and questions in my [first] controlling-pwm-with-Arduino project, I'll ask them all smiley

so first of all: I want program a composition in pwm for both dc motors and big light [say up to 100W or more].

1-- motor: for the dc motor I build an extra circuit for separate power supply according to a circuit which is provided quite a lot the internet
like described here http://www.thebox.myzen.co.uk/Tutorial/Power_Supplies.html
[+ I'd like to add a resistor between source and ground.]
problem: it works [for a long period] without the 1k resistor, with it doesn't do anything. Do I need a lower resistor here? Do I demolish the Arduino and blow up the FET if I don't use a resistor?

2-- I would like to control 3 dc motors. Do I need 3 separate power supplies? [I have 12V/1A amps now]

3-- grounding. How do I make a grounding so that they don't affect eachother? Do I need to make a star grounding for these 3 motorcircuits? Is grounding only direct to the Arduino oké or does it need a piece of metal to drain?

4-- Light. Together with the motors I want to make a dimming composition for light. 3 times again.  I'm not exact sure what kind of light - probably halogen, high Watt.
To also do this with Arduino I think I found a  nice solution for this: a Velleman K8064 kit and a capacitor will do http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1266079091
is it smart to use the same Arduino as for the motors for this?
someone has experience with big lights and this Velleman?

5-- motor/light, motor/light,motor/light stay appr 3 meters from eachother. Is a thin wire from 1 Arduino/circuit/point reasonable?


who does the answers? smiley-wink

thanks!

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[+ I'd like to add a resistor between source and ground.]
Why? What does it do?
That is just going to load the power supply.
Quote
problem: it works [for a long period] without the 1k resistor, with it doesn't do anything.
So you haven't got it where you said. Can you sketch what you have?
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Do I need 3 separate power supplies
No if the one will supply all the current then you can use that. How much current will each motor take?
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Do I need to make a star grounding for these 3 motorcircuits?
It would be a good idea if there is a lot of current around.
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does it need a piece of metal to drain?
No just to the arduino.
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is it smart to use the same Arduino as for the motors for this?
Yes
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Is a thin wire from 1 Arduino/circuit/point reasonable?
It depends on how much current it will take.
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thanks, you're fast!
I made a sketch. and put it here:
http://mariskadegroot.com/wp-content/uploads/2011/10/circuit-motor.pdf
curious what I did WRONGNG



for the extra resistor: I can't remember why, but a helping teacher says so :S.
http://kc.koncon.nl/staff/lex/meetpraktijk/AS_1_2_files/motor-fet.jpg
Because of closing the circuit before the FET?
« Last Edit: October 18, 2011, 01:53:14 pm by riski » Logged

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Assuming that the pin assignment on the FET is correct and it is a logic level FET the only thing I would change is the 1K, make it 100R for a faster switching speed.
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hmm .. a non logic level won't do?
looked it up and I've this one: http://www.digchip.com/datasheets/parts/datasheet/232/IRL520N.php
as soon I get my hands on a little resistor I'll try.

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Do I need 3 separate power supplies
Quote
No if the one will supply all the current then you can use that. How much current will each motor take?
The motors I'll use will have a continuous current of appr 0,7A/12V. so I assume a 1M/12V adapter won't work with 2 motors on full speed?

thanks!
« Last Edit: October 18, 2011, 02:27:12 pm by riski » Logged

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hmm .. a non logic level won't do?
That FET will just about work with 5V, the data sheet says it has an on resistance of 0.22R with a 5V gate voltage at 6A. However it will get hot.

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1M/12V adapter
If that is 1Amp the no it won't do.
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ok. thanks!
I also have these IRF520N
http://parts.digikey.com/1/parts/1019837-mosfet-n-ch-100v-9-7a-220ab-irf520n.html
says: RDS(on) Static Drain-to-Source On-Resistance ––– ––– 0.20 ohm  10V  5.7A
Is this one better or which one should I buy?

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No that one is not as good as the first one as it is not rated for 5V, therefore you would have to drive it with at least a 10V gate signal. To do that from an arduino you would have to use a transistor ahead of the FET.
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