Limit DC voltage draw

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  #1  
Old 07-21-14, 02:48 PM
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Limit DC voltage draw

Hello,

Quick question: is there some way I can limit how much voltage something draws on a power source? For example, can I limit a 24 volt motor to only draw 12 volts from a power source?

The issue I'm having is a motor that takes 12-24 volts tries to suck 24 volts out of a 12-volt power supply. The power supply is reporting "power trouble" as the motor is trying to get 24 volts- something the power supply can't provide. The "fuseless protection monitoring algorithm" then cuts off power. So... what can I do about this?

Thank you all so much for any help you can give me!
If I posted this in the wrong forum section or something, I apologize in advance!

Sam
 
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  #2  
Old 07-21-14, 02:58 PM
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Welcome to the forums.

This forum is fine for your question. You can't restrict a motor from what it needs to start. You can set up a power supply to limit current.

What is it your are working with there ?
 
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Old 07-21-14, 03:04 PM
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Is there some kind of tap change or way to rewire the motor for 12 volts?
Send spec's of motor
Geo
 
  #4  
Old 07-21-14, 03:17 PM
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It's an electric strike. It is used for locking & unlocking doors. An internal motor (I think) does the unlocking.

So basically, when 12 (or 24) volts is sent to the strike, it unlocks. Even a 9 volt battery will make it unlock.

This strike will take up to 24 volts... so what I think is happening is that this strike is trying to get 24 volts from the power supply. The power supply thinks the strike needs 24 volts and cuts power to prevent damage.

So I just need to somehow prevent the strike from being able to try to get 24 volts from the power supply.
 
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Old 07-21-14, 03:53 PM
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More likely from your description id the power supply do4es not has sufficient amps to power the strike and shuts down to protect itself from overload. The solution if that is the case is power supply with a high enough amperage to operate the strike.
 
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Old 07-21-14, 03:57 PM
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Those strikes are supposed to run off a 24vdc power supply. I've worked extensively with them and have found out that they actually work better with 20-22vdc as some overheat and bind up when run on a full 24v supply. The Assa Abloy, in particular like the under voltage.
 
  #7  
Old 07-21-14, 04:03 PM
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The power supply outputs 750mA. The strike is 580mA.
 
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Old 07-21-14, 04:06 PM
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Please see PJ's reply above.
 
  #9  
Old 07-21-14, 04:07 PM
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PJ, it says specifically on the box that it takes 12-24 AC or DC volts at 580mA. It's a Trine Axion 30LC lock, btw.

So the only thing I can do is to get a 24 volt DC adapter? Wiring it into the access control board might be a challenge...
 
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Old 07-21-14, 05:27 PM
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Do you have the LC-100 regulator board for that mechanism. They state it's mandatory.
That strike actually runs on under 10volts.

http://www.trineonline.com/pdfs/inst...tions_2012.pdf
 
  #11  
Old 07-21-14, 06:08 PM
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I don't have the LC-100... crap. Do you think dropping the voltage output from the access controller to 9 volts somehow would work?
 
  #12  
Old 07-21-14, 06:20 PM
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That adapter allows a high strike rate initially (9.5v) and a reduction soon after. You would need to duplicate that to keep that unit from overheating.
 
  #13  
Old 07-21-14, 08:05 PM
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I know a few resistors would be able to drop the voltage, but I have no idea how to drop the voltage again after a few seconds. Is there any quick fix you could think of? Would the strike 'burn out' if it overheated for too long?
 
  #14  
Old 07-21-14, 08:42 PM
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Unfortunately dropping the voltage won't help the motor to strike, the motor needs a less sensitive power supply that can source the inrush current (the motor wants like 2 amps at 12v for a few seconds to kick over, then it needs much less power)

Your power supply has current protection and senses a short when the motor tries to kick on, so it shuts down. A battery basically has infinite current but after a few cycles like that it will run out of power.

You need a 2-stage power supply that acts like a battery for a few seconds then holds like your power supply to keep the lock engaged, which is what the LC-100 does. Using only a battery will only last a few hours and may burn up your motor (hence the many notes stating your warranty will be cancelled if you use anything else.

You might be able to find a cheaper control board but I would recommend going with a controller of some sort intended for that purpose.
 
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