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DC questions.


Guest Scot Meyers

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Guest Scot Meyers

Hey all

As man of you know I have been working 2 projects over the past 2 years my santa scene and my animated band.

well I am at the point of hacking my gemmy animated figures and geting them hooked up to lor boards.

here is my question...

if i use a 9v dc power supply and my motors may be less than 9vdc. will the motor burn up.eventually.

also.

a wall wart power supply has 2wires can someone please help me figure out which wire would be + and which would be -?

and last but not least. i need a little education on reverse oplarity for dc motors.

any help would be sow AMAZINGLY AWESOME in my quest to build my own animations.

thanks

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If you run a DC motor at higher than its rated voltage it MAY burn out. It depends on how much over-voltage it is, but mostly how much load you put on the motor. A lightly loaded motor will probably be fine if only 2 to 3 volts high. Running a 5v motor at 9v with a medium load will probably be too much.

If you have a multimeter, your walwart problem is easy enough. First, though, be SURE it has DC output. Many are actually still AC output.

Cut the wires and strip the leads back some. Put the multimeter on a DC setting higher than the expected voltage. Put the Red lead on one side, the Black lead on the other. If the meter reads +9V then the Red lead is on the Positive side. If it reads -9V, then the Red lead is on the Negative side. If it reads nothing, then the walwart is probably AC output. AC won't read on a DC setting.

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Guest Scot Meyers

JON

THANKS A MILLION!! I will go test my wal warts now I need to make sure because i am using them to power the channel banks of my LOR DC board and i dont want to burn that baby up.

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A DC motor will run at a higher voltage. At some voltage though, the brushes will start to bounce and arch. At this point, the brushes will wear at a much faster rate. Also like a resistor, you have to stay below a certain wattage level. With a higher voltage, the current (and the load) must be less.

Don't you have a volt meter? Just measure it. If the voltage is positive, the black lead will be the negative side. Typically, the wire with the bump or stripe is the negative wire. It's not always true though, so you should measure it.

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Also, many times wall warts will have a little diagram on the front that outlines the polarity of the plug. You'll see + and - labeled on the diagram...I've been buying some good wall warts at the swap meet here locally for 50 cents and $1 each for some of my projects, so if the voltage is too high on yours you might be able to find smaller values pretty cheaply...The current capability of the supply is imprtant as well...

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Hey all

...and last but not least. i need a little education on reverse oplarity for dc motors.

Reversing the polarity on a DC motor will reverse the direction of rotation, assuming it's an ordinary brush-type motor. If it's a high-tech brushless DC motor, then it actually contains (or is used with) a motor controller (chip) and connecting the power backwards will likely do no good. It's extremely likely that your DC motors are ordinary permanent magnet, brush-commutator type motors.

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Guest Scot Meyers

Ok another question. If a gemmy animated bad figure runs at 9vdc for the polar bear and the 2 penquins. would it be safe to say that the 9 vdc is distributed among the 3 figures and if that is the case. How would i know what the VDC would be for each aspect of the figure? the mout. the hips etc. can i devide the 9vdc by lets say 3?

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Wallwarts dont have a red/black wiring.. it's black twinlead, with the pos having a white stripe, neg just being solid black. Ernie said white-striped black is neg.. I'm pretty sure thats the pos + lead.. again, you need to check it with a meter.

Scot, if you have a HarborFreight neaby, they have small multimeters on sale til the end of the month for $2. I have several because they're so inexpensive. If not, you can check RadioShack, but their cheapest is $10. You can try WalMart/Target in the Home Improvement section too.

Edited by skygodtj
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... if you have a HarborFreight neaby, they have small multimeters on sale til the end of the month for $2. I have several because they're so inexpensive. If not, you can check RadioShack, but their cheapest is $10. You can try WalMart/Target in the Home Improvement section too.

If you have a Goodwill or the like near by, you can find various cheap electronics with wall-warts. A lot of people are pitching their old land line phones now a days; a good source of wall-warts.

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Scot, I posted to your other thread re: looking for 120v -> 12v power supplies. Look into using an old PC supply for your 12v, 5v, and 3vdc needs, they at the very least, supply 10amps, and some of the more recent (last 5yrs or so) supply up to 24A. Check ST's page for how to use a pc supply: http://www.scary-terry.com/atxps/atxps.htm. You'll still need a meter tho.

This is the BEST link for using a pc supply: http://web2.murraystate.edu/andy.batts/ps/powersupply.htm

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