I have two of these motors: http://www.radioshack.com/radioshack-super-speed-9-18vdc-hobby-motor/2730256.html#q=motor&start=6&tab=tab1

According to Radioshack's specs (which may be off, not sure), I would need a total of 18v at 4.8 amps, right (I am using an arduino with two of these: http://elcodis.com/parts/6024225/D2394.html#datasheet).

How would I go about this? It is going to be an outdoor project, so I can't use a bench power supply or a desktop PSU. I was hoping to use some sort of laptop charger as they are neatly packaged and I can store it within some sort of plastic if I need to for 'acceptable' weather sealing (it will only be outside when I'm outside, not when it is raining or snowing). Any thoughts?

I am going to be running them at the same time. I don't need an H-Bridge because they are going to be monodirectional. Basically, I will have them turn on, and stay on, in the same direction at the same time. I might make them change speed by using PWM on the arduino, but that is easy (except for the fact that the transistor I have only supplies 100ms max PWM, so I am slightly limited. Thats okay though for this application). I don't mind having it plugged in as well - in fact I would prefer that over a battery. I don't want to have to charge it every time I want to use it. I could run it at 12v (There are plenty of 12v supplies with more then sufficient amperage), but faster is better :P

Any thoughts on where I can get a cheapo 18V 5 amp (sub $10, as that is the remaining budget). Otherwise, I will just go for a 12V and hope it is fast enough.

  • \$\begingroup\$ That's the maximum voltage, but you can also use 12V. I'd use a 12V golf cart battery. \$\endgroup\$ – Samuel Jan 29 '15 at 23:11
  • \$\begingroup\$ You only need 18 volts at 2.4 amps if you want to develop maximum torque. And be advised that if your load is such that you're pulling maximum voltage and current, the motor will overheat very quickly. \$\endgroup\$ – WhatRoughBeast Jan 29 '15 at 23:47
  • \$\begingroup\$ Search for "universal laptop power supply". Perhaps not sub $10, but very close. If you get a $12 one, don't expect the greatest of quality though. \$\endgroup\$ – rioraxe Jan 30 '15 at 21:49

I'd say you can use a standard switch mode power supply to run your Hbridge. Of course, I'm assuming you're wanting to run these bidirectionally. Will they be running at the same time? The reason I ask is because 5A supplies seem to be the sweet spot as far as performance vs cost goes, so you should be in good shape with a 5A supply, if not I'd save some cash and get a lower power supply. As one commentor said, the ratings given are maximums,so you can run them at lower voltage at the price of less torque and slower slew rate. Whatever you decide,take a look at the coil resistance versus the voltage of the supply to make sure you don't exceed their rated current of the windings.


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