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Old 05-03-2005, 11:34 PM   #1
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Default Reducing 12v to 5 v

This may be a stupid question but how can I reduce the 12v from my power supply to 5 volts to run my motor lathe? It can't be too hard can it? Thanks for the help.
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Old 05-03-2005, 11:43 PM   #2
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Get like a 50 turn motor from a smaller motor company. You can plug it directly into a power supply that way. Some might have recommendations on what turn motor to use. 50 turns is close.

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Old 05-03-2005, 11:57 PM   #3
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My motor lathe has a 55T motor but according to Integy, its supposed to use a 7.2v battery. It seems the RPMs are too high with 12 volts.
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Old 05-03-2005, 11:58 PM   #4
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Get a 5V voltage regulator from RadioShack....
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Old 05-04-2005, 12:07 AM   #5
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Anyone into computer case modding will know where to get a fanbus or rheobus. They usually allow you to tune the voltage up and down. Though I am not sure if they can take the current draw.
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Old 05-04-2005, 12:09 AM   #6
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Quote:
Originally posted by SpeedySST
My motor lathe has a 55T motor but according to Integy, its supposed to use a 7.2v battery. It seems the RPMs are too high with 12 volts.
Shouldn't be, unless they didn't design it properly.

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Old 05-04-2005, 01:33 AM   #7
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I use the 55T Integy motor with a 12V power supply. This combination works perfectly.
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Old 05-04-2005, 03:50 AM   #8
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I just use a pack made out of 3 cells with an old stock motor to ruln my lathe. It works great.

If you use a converted computer power supply, it has a 5 volt tap built in already.
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Old 05-04-2005, 11:16 AM   #9
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Seriously, thanks for the replies. I'll just use the 12v supply with the motor. I looked at 5v regulators at Radio Shack and the output is only 1 amp.
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Old 05-04-2005, 11:31 AM   #10
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To do this electronically would get messy since you would have to use either a DC to DC converter or build a pulse width modulator and run it at about 50% duty factor. Another thing that could work would be to use a series resistor. Problem being that you have to know how much current the motor draws while being used to make the calcualtion of the resistance. If you wanted to drop 7 v with a motor that is drawing 5A you would have to use a 1.4 ohm, 35 watt resistor (that is the smallest wattage you could use, better would be 50W). YOu can look around on the web on how to make a pulse width modulator with lm 555 chips, or regular PWM chips. All you would need would be the PWM chip, coupld of FET's and a variable resistor. but just using a smaller supply is the easiest.
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Old 05-04-2005, 02:56 PM   #11
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buying a 80x1 arm and setting the timing to 0 is the easier solution. I use a 55 turn lathe motor, and at 12V it does seem to have too many RPM. I run my Hudy lathe off of a 4 cell pack.
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Old 05-04-2005, 03:42 PM   #12
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You got a motor lathe, isn't it about time you got a charger that does motor run-in's and hence powers lathes? I have no idea what the voltage is on the motor that came with the Hudy lathe I got but I run it at 2 volts cutting with a diamond bit and cuts great!
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Old 05-04-2005, 04:39 PM   #13
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go to www.hobbytalk.com go to the top and look for hobbyshopper. look for the 12volt motor lathe. i use these for the lathe and brush serrator. just hook up to your power supply.
these turn slow enough and will not burn your bit. i bought a heavy duty inline rocker switch. same as on a lamp cord and used 12guage speaker wire. speaker wire is alot cheaper
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Old 05-04-2005, 07:05 PM   #14
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I used to use a Johnson 540 and a 4cell pack for my lathe,

now I use my Team MM motor master to power it,
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Old 05-04-2005, 10:22 PM   #15
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if you want to do a pwm type of deal and alter the duty cycle555lm cmos timer from radio shack. You can reduce the voltage going to the chip to logic level (+5v) with the good ol r-shack voltage regulator which would eliminate the need for a ginourmous resistor. You set the freq by placing resistors and a capacitor across a couple of pins. I used one recently in a voltage multiplier but the concept works for reduction as well. You will need some sort of transistor drive to handle the current going to the motor via a mosfet , you can setup a totem pole arrangement (non-inverting) with an npn/pnp combo of transistors which can be used to drive a mosfet(s). If you want to google non-inverting bi-polar totem pole, you can get a schematic for the driver. The mosfets you just wire in parallel until they handle enough amperage, 3 irf510s (availible at radio shack) should be enough.
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