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Old 11-25-2017, 08:52 PM
sreinmann sreinmann is offline
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Need help with some electronics

So, a break from paper this winter. I知 building a Skunk Works 1/48 scale model RQ-9 Reaper. To coincide with my predator that I modified to display in-flight, I知 doing the same with this kit - but one step further. For this first time ever I知 going to incorporate a pager motor to spin the propeller. This is going to take a lot of modifications and custome work and I think I知 up to that. But, I need some help with the electronics. Nobody in the brick and mortar stores does hobby electronics anymore and on-line stores can only help you buy. Hopefully you can help.

In the aircraft I値l have the motor itself with some pin connectors sticking out of the fuselage. In the base I will have the battery pack featuring 1 or 2, 3V CR 2032 batteries and a switch. Problem one: what component (Resister?) do I need to add to the circuit to limit the voltage. I don稚 know how fast will be too fast. 6V combined sounds too fast. Second: what component would I add that could not only turn power on/off, but also regulate the power (column knob) so that I could spin it fast or slow. If I knew what to ask for, at least I could shop more coherently.

Thanks in advance.
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Old 11-25-2017, 11:30 PM
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Jim Nunn Jim Nunn is offline
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sreinmann
I need a little more information before I can answer your question accurately. What I would need to know is how much current the motor draws at a given voltage.

If you haven't purchased a motor I have listed a couple of motors from All Electronics

https://www.allelectronics.com/item/...ibrator/1.html

https://www.allelectronics.com/item/...i-motor/1.html

https://www.allelectronics.com/item/...i-motor/1.html

The third motor is rated to operate at 8100 RPM (way to high) at 6 volts and draws 36 milliamps (mA).

assuming the speed to voltage curve is linier (and it is not) running at 3 volts the speed should be 4000 Rpm and at 1.5 volts around 2000 RPM. So by simply switching between batteries you have some speed control but 2000 RPM may be too high.

Using resistors you may have to do this by trial and error. for a 3 to 6 Volt motor I would purchase two 20 ohm two 10 Ohm, two 5 Ohm and perhaps four 1 ohm 1 Watt resistors. By wiring these in series with the motor , by trial and error you should find a resistance that works. I'm thinking that with 1.5 volt battery the motor may run to fast. So two 20 Ohm resisters is series should cut the voltage to the motor to about half. but that may still be too high. Just add a 10 ohm in series. keep adding the resistors in series until you get the speed you want. As with the batteries adding a switch will give you some preset speeds.

There are small DC motor controls if you decide to try and use one I would suggest that it is a PWM controller. There are some "Kits" for these but you need to be skilled with a soldering Iron and working on printed circuit boards. If not find a friend who can do the soldering for you.

Small motors do not tend to run at slow speeds very well. This has to do with how the armature is designed and how many magnetic poles the motor has.

If you have any questions you may send me a private message and I will answer a soon as I can.

Jim Nunn
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Old 11-26-2017, 10:43 AM
sreinmann sreinmann is offline
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Ok great. More specifics. The motor O have was salvaged from a quad copter. It is probAbly a DC 1.5V 30000RPM 716 Motor
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