How do I convert 10 to 24 volts dc input to 6 vdc output?

[PRW]

I have an application using a 24VDC/20AMP permanent magnet 56C faced motor coupled to a reducer. I want to add a spring actuated/electrically released brake between them. The problem is, my customer wants to run the motor at different voltages to get different output speeds at the reducer.
The brakes I am looking at are available with 6, 12 or 24 volt coils. Since the customer is using voltages from 10 to 24, I can't use these brakes as supplied, since they only allow plus or minus 10% voltage input.
So I wondered if those different input voltages, 10 to 24, could be converted to a steady 6 volt dc output. I could then use the brake with the 6 volt coil, which is rated under 2 amps.
Is this easy to do?

 

[waross]

Se if the controller has a dry contact that can be used to control the brakes.
Look for a relay that will operate on a wide range of voltages.
Use a relay and a light bulb to ballast the relay coil and extend the normal operating range.
Use a relay with a series resistor and a Zener diode.
There used to be a delightful line in our code book that suggested that difficult code applications may often be solved "Through the exercise of ingenuity." That may be needed to solve this problem.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[BobM3]

If you're going to pull power from the 20 amp supply, make sure you have enough amps available for the brake. Smaller voltage brakes will need larger currents. How much current do you need for the brake?

 

[itsmoked]

Perhaps something like this:

http://www.cui.com/pdffiles/PTK15-T series.pdf

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Or power the brake from whatever constant power supply you have - battery? mains? - and switch the supply to the brake using a solid state relay. DC input types usually accept anything from 3V to 32V as a control voltage. Things to watch with SSR's: heatsinking; overloads more than a few seconds in duration; fuse sizing; transient protection.


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If we learn from our mistakes I'm getting a great education!

 

[PRW]

Thanks you all for your input. I think I have to add some more information so you can see that there are some limitations that would prevent me from using your input.
The motor is rated 24VDC at 20 amps. The power supply has enough output to run 10 of these units simultaneously.
The application has only two leads available, the ones going to the motor/reducer. I can add no more, so I have to wire the brake in parallel with the motor. With that in mind, I need something between the motor and the brake wiring. Perhaps the device Keith mentioned is something I should consider. I will contact the manufacturer for their input.
If this doesn't make sense, please let me know.

Thanks again, Paul

 

[OperaHouse]

I had a similar application for a pump motor running on a VFD where the voltage changed and it had to run a valve. Only the motor wires were available. I used a wide range switching power supply.

There are switching power supplies which convert 10 to 24V DC to a voltage like 6V DC. Depending on the application and the power supply, you may need a relay (powered off the 6V)in series with the motor to prevent motor lock up when power is first applied.

 

[PRW]

Thanks OperaHouse, can you recommend some suppliers? I tried a google search, but did not find what you were talking about that would fit.

 

[OperaHouse]

No one can suggest anything without the voltage and current of the brake being supplied.

 

[itsmoked]

PRW; Is this just a one-off, or production for many units? The reason I ask, is that, there are probably less expensive ways to do this than just an off-the-shelf DC-DC but they would cost something to design. For instance there are a lot of switching regulators, instead of full on DC-DC converters, that would do the trick but they're not appropriate to field wire by themselves.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[PRW]

Well it now looks like I will have to use the 12 VDC brake, not the 6 VDC. The 12 VDC unit has an inrush of 25.9 and holding of .5 amps.

To answer Keith, this is for 10 motor driven plating barrels. They connect to power when they are lowered into the tank. When they are removed, the brake will be spring applied. Whet ever is done to control the brake will be on the barrel, under cover.

 

[OperaHouse]

That seems like a lot of current, doubt the brake could take that much current continuously. That may rule out a standard power supply. I assume you are supposed to pulse it for a short period of time with high current and use a circuit to lower current for long hold in periods. I've built solenoid drivers like this, prototypes that never went into production. Check that specification again because you may not have a solution.

 

[PRW]

The continuous is the .5 amps mentioned above. Why wouldn't a standard power supply work?

 

[OperaHouse]

Magnetic field decreases with the square of the distance. The amount of current needed is much less when the gap closes. This can be accomplished two ways. (1)A circuit with a large capacitor that has a large amount of stored energy to dump or pulse current limiter. or (2)The brake has two coils. One a low current hold in and a second high current pull in that disengages after it is pulled in. I have seen the two coil system in large DC contactors. I can't imagine this in a brake because these are tricky enough to set just the gap. That would be a real safety issue. The information you have given me is just not detailed enough to provide a solution. It just sounds wrong. Suggest a talk with the manufacturer for a solution.

 

[roydm]

Sounds a bit like the brakes I worked on as an apprentice, Coles and Rapier Diesel Electric cranes. These had the brake coils in series with the motor. Perhaps you could use a 6 Volt unit in parallel with a 6 Volt Zenner in series with the motor or re-wind the brake coil with heavier wire.