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We're trying to rig 6 bundles of 10 motors at a time, so 60 motors in total on the same power supply. Each one normally is directly powered with 1.5v aa battery.
We read the current as 200ma per motor.

PS. I am dyslexic, and have severe learning disabilities. Forgive any grammar and punctuation issues.

Autistic
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adam ketteringham
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2 Answers2

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So, I'll make this simple. If the motors are paralleled with the supply then the current adds, if they are in series the the voltage adds together.

If I have 1.5V motor that draws 200mA, I need a 1.5V power supply that can output at least 200mA, I could use a 400mA supply and the motor would still draw 200mA (assuming the power supply is regulated). You can also calculate the power P=I*V, power= current * voltage, 0.3watts = 0.200 Amps (or 200mA) * 1.5V

If I have two 1.5V motors that each draw 200mA there are two configurations I could put them in. I could put them in series or in parallel. In series I need a 3V supply, and each motor will still draw the 200mA it needs. In parallel I need a twice the current. I can still use a 1.5V supply, but I need 400mA of current.

schematic

simulate this circuit – Schematic created using CircuitLab

If you have 6 motors in series, you need a 1.5V*6(motors) = 9V supply that will draw 200mA If you have 6 motors in parallel, you need a 1.5V supply that will source 6*200mA = 1200mA or 1.2Amps

If you had 60 motors you could make 10 strings of 6 motors in series (I can draw this if you'd like, but only if you request it) So you could make 10 paralleled strings of 6 motors each. A 9V supply would work, but each string would need 200mA and you have 10 strings so you would need a 9V supply with each string drawing 200mA*10 = 2000mA or 2Amps so a 9V supply with 2 Amps should work.

Voltage Spike
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  • Thank you, also in this case of a series then, I'm going to need to connect 10 wires to the positive of the power supple and 10 back to the return , is there any connector blocks that do this? – adam ketteringham Feb 10 '16 at 19:35
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    Motor strings in parallel try to maintain constant speed at each motor. In series, they act more like an automotive differential- load one and it slows down a lot, and the other lightly loaded one speeds up a lot. – Spehro Pefhany Feb 10 '16 at 19:38
  • so which circuit os best, the parallel, even though it requires more current ? – adam ketteringham Feb 10 '16 at 19:46
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    Both circuits require the same amount of power, one just has higher voltage, while the other has higher current. If your motors will have different loads (one motor might have higher load) it would be better to parallel them all. I feel like mathematically this answer is good, but as far as usefulness Spehro's answer is better. – I. Wolfe Feb 10 '16 at 19:50
  • @adamketteringham domestic terminal blocks are probably the easy answer http://www.maplin.co.uk/p/3a-terminal-blocks-3-pack-l96ar – pjc50 Feb 10 '16 at 21:22
  • I'm assuming the motor was tested under load, the load will change things. Do you really think a motor that is normally powered by a battery will draw 1.8W as Sphero suggests? on a 2500mah battery it wouldn't last long. With a regulated supply you may have a voltage drop on startup, it is not something to be worried about, the motors will turn. You don't need 600% Margin – Voltage Spike Feb 10 '16 at 21:27
  • @laptop2d - "Do you really think a motor that is normally powered by a battery will draw 1.8W as Sphero suggests? " Absolutely. Lock the rotor in place and watch what happens. The phenomenon is called stall current. In normal operation the rotor will begin to spin and the back EMF will reduce the current, but that is not what Sphero is talking about. At the instant of turn-on it's stall current that counts, and in general a DC power supply (rather than a battery) will deal with overcurrent by grossly reducing output voltage. If it has foldback limiting you're out of luck. – WhatRoughBeast Feb 11 '16 at 01:47
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If the motors are all going to be heavily loaded you could need as much as 12A @1.5V plus more for starting (so if they start all at once, the surge is maximum, if they are staggered start-up then not so bad).

I would suggest using a safety-agency approved 19V laptop adapter with one or more step-down buck regulator modules set to 1.5V (the laptop adapter takes you from mains voltage to 19V and provides isolation and safety, the step-down modules give you the actual voltage you need).

If you are doing groups of 6 you could use one LM2596 module for each group, or there are ones capable of 12A out.

The total power consumption of the motors is only 12W so almost any laptop or netbook adapter will work (most are good for 60-90W).

Be sure to set and/or confirm the output voltage before connecting the motors.

Spehro Pefhany
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