12v dc speed controller?

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jimmy mack

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hi, i am about to build a drag lure machine and have been looking at the current set ups which use the following:

12v battery/car starter motor and a solenoid

the solenoid is simply switched on/off to control the lure.

there is not much load on the starter, it is fitted with a plastic spool which holds the line for the lure, the lure is also very light.

I would like to ask the best way to accurately control the speed of the motor as the current method (solenoid) is either stop/go.

Perhaps a 12v DC speed controller or high power rheostat capable of dealing with the amps drawn form the starter (not sure what amount)

I hope this makes sense and i look forward to any suggestions given,if anyone can supply links to suitable units, then it would be much appreciated, thanks guys!

here is a pic of the most widely used type of lure machine, this type of set up has been used for years and i just wondered if the lure speed could be controlled accurately?

12v battery/car starter/solenoid

**broken link removed**
 
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OK, just out of curiosity, why would you want to use a high-torque, high-current starter motor to pull a very light lure. Sort of like trimming you fingernails with a chainsaw.

Ken
 
KMoffett said:
OK, just out of curiosity, why would you want to use a high-torque, high-current starter motor to pull a very light lure. Sort of like trimming you fingernails with a chainsaw.

Ken
Click to expand...

Hi Ken, most of the set ups i have looked at use this type of motor with a solenoid to turn on and off the motor to control the lure movement. I would like to be able to have more control over the speed of the lure and this is why i am asking for ideas. I am also open to suggestions as to a better way to go about this. thanks.
 
I'm not a fisherman..though I have spent time washing worms in the past. Don't know if I have any answers, but am interested in the problem. What's the weight of the line? Whats the size of the spool? How much line is payed out? How fast are you trying to retrieve the line/lure?

Ken
 

Sorry Ken, forgot to mention this type of lure machine is used in sighthound training, the spools used can vary. (one in pic is a reel from a mig welder)

The line is usually polyester or nylon around 2mm and speed can be around the 50mph mark.
 
For starters, I agree with the previous posters that the starter motor is not well suited for this task. It is designed to deliver huge torque at relatively low speeds, and your requirements are for much less torque at much higher speeds. If you can find a suitable motor, you will find that the task of building a speed controller will get much easier because it will be Pulse Width Modulating(PWM) 2 to 3A vs 20 to 50A.

Coming up with a PWM is highly dependant on the motor you are controlling, so find a motor first...
 
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For an 6" dia. coil on a spool:
50MPH=165876"/min
165876"/(6"*Π)=8800 RPM

I can see why they use starter motors. How slow do you want to go?

Ken
 
KMoffett said:
For an 6" dia. coil on a spool:
50MPH=165876"/min
165876"/(6"*Π)=8800 RPM

I can see why they use starter motors. How slow do you want to go?

Ken
Click to expand...

once the lure is moving, it is all about keeping it just in front of the dog, i think the set up in the pic would run around the 45/50 mph mark.I think the spool most used with the above set up is around 4"dia.
 
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If the coil diameter is 4" then you would need to be running 13500 RPM for 50MPH.

Where do you stand when this thing ramps up the speed. The horizontal gyroscopic torque has got to be trying to spin that stand. That switch cord doesn't look nearly lock enough to me.

Ken
 

It is pretty stable, although you can peg it down if you wish. The cord length varies, as almost all of these machines are custom made.
 
That's an interesting application for a standard starter motor. What's the current draw? I'll take a guess it's only 10 to 30 A.

Starter motor is series-wound, meaning it's optimised for higher torque for stalled loads, like engines. Motor of this type is not easily speed controlled, you'd need parallel wound instead and then apply a constant voltage.

One way of adding a speed control is to fit a tacho somehow, and then using that to vary the current in the motor. Could probably just use something crude like a centrifugally operated transistor switch to cut power to the motor.
 
thanks for all the help guys.

On another note, any recommendations as to a good 12v battery for this purpose (the lighter the better?)
 
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Motorcycle starting battery is a scaled-down car starting battery, eveything is scaled down the weight, starting amps and of course the useful life you get. It still loses capacity at the same rate when deep discharged. If a 60 A/hr battery gives you an hour's use then a 30 Ahr one will give you 1/2 hr use, probably a lot less, because the higher depth of discharge causes the bettery to fail quicker.


 
Hello

Hi jimmy
This is ram studying mtech III sem digital communiatin and networkin i m searching for project on vlsi and embedded systems can u pls suggest me n thank u
 
I've read all the replies to your post,and there is a lot to be considered before you go any further,if you still want to experiment with the starter motor,then you will have to build a PWM that can cope with the ampage draw,or you will 'fry' it.I would suggest a smaller dc motor similar to the electric car seat motors,and a bi-directional PWM OR A convental PWM controlled by relays for reversing.Another problem is the battery going flat.I've buit a system similar to your requirements to open a garage door,controlled by a pot to start slow and increase speed as required.When building a PWM you will have to ensure it will cope with constant running,(many pwms fail if they are under rated.You cannot control the motor with just a potentiometer or rheostat,they will burn out.
 
hi i just tried to buy a computer jigging reel from www dolfingfishing.gr but they stopped making them. i can get all the mecanical parts for the reel its the design and building of the controls thats the problem for me. although the finished product would be a viable commercial proposition i only need two for the fishing boat i am fitting out to fish from port antonio jamaica. any help or ideas wold be appreciated
manxrover ps two other examples beltonic bj 5000 and dng in iceland
 
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