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So this question is for anyone out there with some electronic skills again to help me out before I go and kill myself with volts and amps and omhs.
This is a diagram of what I believe will be the curcuit I can use, I have the switch, the motor and the battery (not yet purchased), so does this look right to all you keen observists out there?
The motor has just 2 connected on it one black one white, and the switch is brand new so there are no markings on it... how do I tell which side is which?
What kind of battery(ies) should I be using? Any resistors?
I don't want it to spin too fast, I want a nice smooth maybe a turn every few seconds? possibly a little faster than that.
EDIT: I was sort of in a rush and not sure of the side of the battery on the diagram, but I will be using it the right way when I make the actual circuit.
Last edited by omgitsduane; July 17th, 2008 at 08:08.
You can't really hook a permanent magnet DC motor up "backwards", it will just spin in the other direction =).
When you hook it up to the battery it will spin at a fixed speed based on the properties of the motor and voltage of the battery. If you want to control the speed, you need a regulator. This can be accomplished with resistors, but that wastes battery power. Any number of parts are readily available (e.g., the classic goto guy LM317). Honestly it's probably best to just drop a couple dollars on a cheap model train controller.
First of all your battery may technically be backwards in your diagram (it's been a year, so sue me) but other than that you're fine (and as IAffe says all that will happen is you'll spin backwards). Secondly the rest of my post is long winded and redundant after IAffe's so only read it if you really want to read everything I wrote or for some reason don't like his solution.
As for the battery pretty much anything will work, bigger batteries (voltage wise) will spin faster. If you only need a revolution every few seconds (depending on your motor) you might even be able to make do with something as small as a watch or hearing aid battery. I suggest just buy whatever fits your model that you can get on the cheap.
Secondly a disclaimer about the rest of my post. I have only some experience with electronics and so much of what I'm suggesting comes from combining my electromagnetism class with my experience working on my computer. If the items I'm describing don't exist on the scale needed here please feel free to correct my suggestions (I'm thinking specifically of a voltage regulator which I know exists for computer fans and I assume exist in multiple sizes as well.) I am not an Electrical Engineer and circuits is something I only know a little about, if I'm saying dumb things correct them please.
In terms of controlling the speed of the motor there's 3 easy ways to do it, one medium way and one hard way.
The 3 easy ways are:
1) Buy a motor that rotates the speed you want it to with the voltage and amperage coming out of your battery(this will require you accept a certain range and shop around a lot for motors and batteries).
2) Attach an additional voltage regulator to the circuit. You should be able to find these in an electronics\hobby shop, look around your area and talk to the owners see what they have and can get you. Basically you'll just slap that badboy in between your switch and motor and can use it to fine-tune how fast the motor runs
3) Buy an integrated voltage regulator\switch. Same thing as above just you replace the switch entirely. Keep in mind that you can have redundant switches with no issues.
All of these methods are simple, take up very little space and just require soldering an extra piece in place. (if that)
The medium way is gears. If you're having trouble finding the electronics, or you aren't really certain about what you have in terms of your setup you can always use gears to slow down the RPMs on your piece. Go from an ittybitty gear on the motor to a huge one on the piece that's rotating to slow down the motion, or vice versa to speed it up. (hopefully my dyslexia didn't flip the order on those so someone a little more awake double check that I did the step up step down right).
This is the medium way because the gear ratio might be difficult to calculate\require lots of trial and error. Depending on how fast the motor is and how fast you want it to be it may require going up to gears that are too large for our (your) models. Finally, it may be a pain in the but to find and position gears so that they properly mesh. The advantage of course is it's all things you can see and touch and (in my opinion) might be easier to do than finding a regulator sized for your model.
The hard way I only know about in theory. In theory you could attach a chain of capacitors going from the switch to the motor, and by using the size and charge rates and other much more complicated things I don't know much about, you should be able to slow down the motor if you really wanted to. I have absolutely no idea how you would set this up but in theory it should be possible. Any double E's (Electrical Engineers) who feel like walking people through that can feel free, I wouldn't want to mess with it myself.
Regardless of how you wind up doing it, I'm impressed that you're even trying Duane, make sure you give us WIPs (including soldering burns of course) as you go through this.
Last edited by paul_Harkonen; July 17th, 2008 at 07:16.
~2k of genestealery goodness
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Dovie'andi se tovya sagain
more witty remarks to come.
Simple switches like that one have no sides. It will work regardless of which end is connected to + and which to the -.the switch is brand new so there are no markings on it... how do I tell which side is which?
And I should have put a resistor in there, but I'm still trying to understand HOW to judge what is the best size resistor to use.
I was told today that a variable switch is probably my best bet, so after some research I'll make my decision.
And on top of that, I found out the switch I bought (as perfect as it was for me) wouldn't work how I thought, as it would only work when held down, which I don't want as that removes the fun of having a pump run by itself.
You can purchase motors which have a step-down mechanism built in, which step down via a series of gears that just slot over the drive shaft. A potentiometer would do well to reduce the speed as well, as well as putting a small lamp in series with the motor, as lamps have a high resistance, and hence have a large voltage drop across them, so will help to regulate the speed as well. Make sure the motor is a DC motor like from a small radio controlled car, not an AC motor like in a mini-drill....
Well I've just found what I need on the internet, all the motors I have would require so much power its just not worth it. So I've tracked down one that runs at 3v but can goto 4.5, but since the load will be barely anything, I doubt it will slow it down much.