several quiestions controlling dc motor [together with controlling light]

ok. because come across several little problems and questions in my [first] controlling-pwm-with-Arduino project, I'll ask them all :)

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? ;)

thanks!

[+ 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.

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?

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?

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.

does it need a piece of metal to drain?

No just to the arduino.

is it smart to use the same Arduino as for the motors for this?

Yes

Is a thin wire from 1 Arduino/circuit/point reasonable?

It depends on how much current it will take.

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?

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.

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.

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?

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!

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.

1M/12V adapter

If that is 1Amp the no it won't do.

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?

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.