Hi all ,
Wondering if anyone here can help me with a bit of advice .
I have a small electric motor that I have put on a rod turner . The motor is rated for 3v and runs thru a set of gears to reduce the speed at the output shaft .
Works fine at 3 volts but it runs to fast and i need to reduce the voltage to 1.5v to achieve the speed I need . The young "expert" at Jaycar today sold me a resistor to put in the pos lead to the motor to reduce the voltage to 1.5 . Problem is when I soldered the resister inline it let no power thru at all .
The numbers on the resistor are 10w27ohmJ .
Any ideas how I can reduce 3 v to 1.5 ?
Cheers Al
Don't use a resistor.
Instead use a PWM controller (pulse width modulation). I typically buy these from Ebay.
I won't bore you with the details of these except to say you will get a continuously variable speed from your motor so you can dial in the right speed.
Units like this will do the job:
https://www.ebay.com/itm/DC-New-1-8V-3V-5V-6V-12V-2A-Low-Voltage-Motor-Speed-Controller-PWM-1803B/172785981506?hash=item283ad8d842:g:~z4AAOSwsMVZbwYQ
or
https://www.ebay.com/itm/3V-35V-12V-24V-5A-PWM-DC-Motor-Speed-Controller-Adjustable-Switch-LED-Fan-Dimmer/122943366971?epid=918271106&hash=item1c9ffee73b:g:VfYAAOSw7GRZKUR2
Anything like those will do the job. As you are only using 3v just make sure that your pwm controller can work with that.
Awesome TB , how bloody cheap are they eh .
So just to be sure , if I get this one
DC 1.8V 3V 5V 6V 12V 2A motor speed controller 30W PWM 1803b K7 L6
And say input 6v I will be able to turn it down to 1.8 v , do I understand that correctly ?
Thanks heaps .
Why not just get one of these?
https://www.ebay.com/itm/New-110V-100W-7000RPM-Home-Sewing-Machine-Black-Motor-With-Foot-Control-Pedal/252783003505?hash=item3adb0a8771:g:1ZkAAOSw4A5YrflC
(https://www.ebay.com/itm/New-110V-100W-7000RPM-Home-Sewing-Machine-Black-Motor-With-Foot-Control-Pedal/252783003505?hash=item3adb0a8771:g:1ZkAAOSw4A5YrflC)
https://www.ebay.com/itm/Singer-242-motor-light-and-foot-controller-working/302626503397?hash=item4675f1fae5:g:SvQAAOSwXOhadd~z (https://www.ebay.com/itm/Singer-242-motor-light-and-foot-controller-working/302626503397?hash=item4675f1fae5:g:SvQAAOSwXOhadd~z)
Quote from: swoffer on February 07, 2018, 01:23:07 PM
Awesome TB , how bloody cheap are they eh .
So just to be sure , if I get this one
DC 1.8V 3V 5V 6V 12V 2A motor speed controller 30W PWM 1803b K7 L6
And say input 6v I will be able to turn it down to 1.8 v , do I understand that correctly ?
Thanks heaps .
AC and DC motors work very different. A DC motor will not work if you reduce the voltage. It will only work at the proper voltage rating of the motor (+/- tolerances). What drives the motor faster or slower is the effective overall current provided to the motor. Note that the motor will only take a maximum prescribed current and you cannot push more current to make the motor faster even if you wanted to. What a PWM device does it controls the amount of pulse current going to the motor. The closer the pulses are together, the faster the motor will operate. The wider the time between pulses will slow the motor. In short, the speed of the motor is controlled by the current, not the voltage.
Thanks Bryan , I think I get what you are saying . But in laymans terms for me , if I get this little gadget will it control the speed of the motor I'm using ?
Quote from: Keta on February 07, 2018, 01:55:33 PM
Why not just get one of these?
https://www.ebay.com/itm/New-110V-100W-7000RPM-Home-Sewing-Machine-Black-Motor-With-Foot-Control-Pedal/252783003505?hash=item3adb0a8771:g:1ZkAAOSw4A5YrflC
(https://www.ebay.com/itm/New-110V-100W-7000RPM-Home-Sewing-Machine-Black-Motor-With-Foot-Control-Pedal/252783003505?hash=item3adb0a8771:g:1ZkAAOSw4A5YrflC)
https://www.ebay.com/itm/Singer-242-motor-light-and-foot-controller-working/302626503397?hash=item4675f1fae5:g:SvQAAOSwXOhadd~z (https://www.ebay.com/itm/Singer-242-motor-light-and-foot-controller-working/302626503397?hash=item4675f1fae5:g:SvQAAOSwXOhadd~z)
Yeh , cheers , these setups obviously do work for this , plenty have used them .
But I already have the setup complete with the motor I have so I'm just trying to work with what I've already got .
Quote from: swoffer on February 07, 2018, 02:28:21 PM
Thanks Bryan , I think I get what you are saying . But in laymans terms for me , if I get this little gadget will it control the speed of the motor I'm using ?
Picture one of those water wheels that use to turn machine back in the old days. A directed stream, water goes into a trough. The water is then emptied onto a water wheel with little buckets to catch the water. The more water you put in the buckets, the wheel starts to turn due to gravity. The faster or more water is added to the wheel, the faster the wheel turns. Does this makes sense? I may be explaining it all wrong.
Yeh ,nah , its clear as mud now ;D
See , I'm even more confused now . When I picked up this motor it is clearly marked for 3v . When I ran 3v to it from a power supply it ran at about 50rpm . So I got a 1.5v d cell and wired it to the motor , it then ran fine and about 10rpm , which is what I'm looking for . But if I read your first post correctly Bryan it shouldnt have worked on 1.5v ?
I hasten to add that I am extremely tech challenged when it comes to electronics :'( :'( :'(
Swoffer - if it's 3v motor (I assume DC) then apply the 3v to the pwm controller, don't use 6v, it's too much. The ouput of the controller connects to the motor. A pwm controller doesn't change the voltage so the output would still be 3v. What happens is the controller 'chops up' the 3v at a high frequency, typically 10kHz to 50kHz. When you adjust the knob it varies the duty cycle, ie it is swiching on and off very quickly. So it is either 3v or 0v. The more times it is at 3v the faster the motor goes. The motor averages it's speed dependant upon this duty cycle but still maintains high torque as if it were on 3v all the time. If you were to simply lower the volatge the torque drops - ie the motor ends up being 'gutless' and not able to do its job.
The PWM controller is the way to go ;)
After going through all the monkey motion you will still have a motor that you can not easily control the speed of without using your hands. Reinventing the wheel seldom improves things.
Quote from: swoffer on February 07, 2018, 02:50:13 PM
Yeh ,nah , its clear as mud now ;D
See , I'm even more confused now . When I picked up this motor it is clearly marked for 3v . When I ran 3v to it from a power supply it ran at about 50rpm . So I got a 1.5v d cell and wired it to the motor , it then ran fine and about 10rpm , which is what I'm looking for . But if I read your first post correctly Bryan it shouldnt have worked on 1.5v ?
I hasten to add that I am extremely tech challenged when it comes to electronics :'( :'( :'(
Likely the D-cell voltage is within it's tolerance, but the current draw is significantly less...thereby slower running motor.
Dc motor speed is voltage dependant for a given rotor/magnet combination. If you don't need torque, aka start up power, dropping the voltage will reduce speed. If your rod turner is just for drying epoxy you don't need much power. If it's for power wrapping/cork turning etc. you do need a bit of power. My take is - build a machine that will do both with variable speed - one machine many uses. Wrap your guides with speed - then turn down the revs apply epoxy and leave to dry. This is why I would go for a manual speed control - dial it up - leave it alone to dry.
As always your choice :)
If the rod turner is for wrapping then you need some torque and either a good slip clutch or a foot control like Lee has shown. If the rod turner is for drying then you don't need much torque but fixed speed control is important to keep from flinging off the finish before it dries. For drying, the modulator like Tiddler has shown may work best. Trying to control it by varying the voltage never works well because the speed and the torque interact and it may take many attempts before you find the right voltage.
Personally, I'd just toss it and get a little 10 rpm gear motor.
https://www.ebay.com/itm/DC-12V-0-6-120RPM-Reversible-High-Torque-Turbo-Worm-Electric-Geared-Motor-USEFUL/122297766357?hash=item1c7983d1d5:m:mybqDXTYEleucwD9w5MtURg (https://www.ebay.com/itm/DC-12V-0-6-120RPM-Reversible-High-Torque-Turbo-Worm-Electric-Geared-Motor-USEFUL/122297766357?hash=item1c7983d1d5:m:mybqDXTYEleucwD9w5MtURg)
Sorry, I'm posting on top of Tiddler.
-steve
So it's a DC(direct current, i.e. usually battery operated only)) motor? Or does it plug into household current(AC) and use a converter(a converter reduces volts("force or pressure" of electricity) and the amperage(flow of electricity as a rate i.e. # of Charged particals movin across a conductor/unit of time) and converts AC to DC.
That resistor they sold you, can it be installed one way only? Or maybe it dosen't matter?...
Good tool to have is Digital Multi-Meter. You can measure dc or ac volts, small volumes of amperage, resistance(ohms), etc., etc.
Gfish
Resistors are not polarity sensitive. You can fit them whichever way round - they just have a very limited function - they resist.
For a VERY simple explanation of electricity.
Think of plumbing.
Hold a pipe vertically - the distance in height from one end to another is similar to voltage - a potential difference.
Water will flow more quickly through a vertical pipe than one near the horizontal = more voltage means more current for a given wire (pipe)
Now increase the bore of the pipe = less resistance more flow = less resistance more current - amps.
Greate pressure of water - more volts = greater flow = more amps
Simple equations Ohm's Law - Volts (V) = Resistance (R) x Amps (A) or A = V/I or R = V/I also Power (simplified) = V x I
Cool. Good visual explaination. Missed what "I" was. Is it = to Watts. Good to know 'bout resistors. Sorry for the thread tangent, Swoffer.
Gfish
Gfish, there's no need for a converter. A bridge rectifier does the job of converting the AC to DC.
................Lou
AH , thanks so much for all the input guys .
Ive got my head around how these PWMs work now .
I've ordered one off Ebay , $1.72 with free postage , unfreekin believable how they can do it for the price .
Anyway I'll try it and see .
Again thanks for the pointers , I knew I would get good advice here .
Swoffer - the price thing is easy - big country - billions of people - they make a few cents on each product - they are all trying to make money. Every country has done it at some time or another :-\
The point is it will do the job :)
Brian has to be correct. If he is using a 3 volt power supply then it's almost got to be a dc motor. An idea, buy a charger and some rechargeable D cells. You know they give you what you want.
Ron
Ron - my rod wrapper was originally battery powered. Until I finished wrapping some guides - I set the motor speed to slow applied the epoxy and left overnight to set. The batteries died in the night. The epoxy sagged and dripped. It was a royal pita to clean up and redo. After that I fitted a mains power pack.
Quote from: Tiddlerbasher on February 08, 2018, 11:42:27 AM
The batteries died in the night. The epoxy sagged and dripped.
Yep , my biggest concern as well with the battery option .
Quote from: Bryan Young on February 07, 2018, 02:16:54 PM
Quote from: swoffer on February 07, 2018, 01:23:07 PM
Awesome TB , how bloody cheap are they eh .
So just to be sure , if I get this one
DC 1.8V 3V 5V 6V 12V 2A motor speed controller 30W PWM 1803b K7 L6
And say input 6v I will be able to turn it down to 1.8 v , do I understand that correctly ?
Thanks heaps .
AC and DC motors work very different. A DC motor will not work if you reduce the voltage. It will only work at the proper voltage rating of the motor (+/- tolerances). What drives the motor faster or slower is the effective overall current provided to the motor. Note that the motor will only take a maximum prescribed current and you cannot push more current to make the motor faster even if you wanted to. What a PWM device does it controls the amount of pulse current going to the motor. The closer the pulses are together, the faster the motor will operate. The wider the time between pulses will slow the motor. In short, the speed of the motor is controlled by the current, not the voltage.
Just to be clear on this, in a DC motor, voltage determines rpm, and amperage determines torque.
In an AC motor, frequency determines rpm, and amperage determines torque.
Quote from: Three se7ens on March 14, 2018, 04:25:39 AM
A DC motor will not work if you reduce the voltage. It will only work at the proper voltage rating of the motor (+/- tolerances).
Hmmmm , dont know about this as I'm not a sparkatron at all , what I do know is the motor is rated for 3 volts and running it on 1.5 v caused it to run fine just at 1/3 the revs of 3 volts .
Any way I got the little modulator thingy in the post the other day , wired it in and it works perfectly . It has a dial on it that allows the rod turner to run at any revs I want from 0 to 50 . So in the end its just what I needed .
Cheers for the input guys .
Al
Print a copy and put it in your files... I refer to this regularly.. Carl, KF5SPZ..
So what I see and hear is waay cool(good)... first thing is in watching the post I've learned stuff, the question was answered, you learn something, The price is right! Thanks again to all of the people who have made this forum work. And work well.....🙏🙏
I'm glad it is working. I never thought I'd see the day where a PWM would be as cheap as a potentiometer. Really, anything would do that would change voltage to the minimum that will spin the motor will do. 3-7s is absolutely correct, a DC motor will only spin in its designed voltage range, but I have been surprised often at how wide that range is.
Glad it all worked out.
NOW SHOW US PICTURES OF YOUR WRAPPED RODS!!!
Ron
Quote from: swoffer on March 14, 2018, 07:43:06 AM
Quote from: Three se7ens on March 14, 2018, 04:25:39 AM
A DC motor will not work if you reduce the voltage. It will only work at the proper voltage rating of the motor (+/- tolerances).
Hmmmm , dont know about this as I'm not a sparkatron at all , what I do know is the motor is rated for 3 volts and running it on 1.5 v caused it to run fine just at 1/3 the revs of 3 volts .
Any way I got the little modulator thingy in the post the other day , wired it in and it works perfectly . It has a dial on it that allows the rod turner to run at any revs I want from 0 to 50 . So in the end its just what I needed .
Cheers for the input guys .
Al
Sorry, I did not say that part. I just had the message quoted wrong. Its fixed now