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To design a 24Vdc to 42Vdc motor ciruit

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wongkongwai

New Member
Hi Friends,

I would like to design a motor circuit for my project. Hope that you guys can help. This motor circuit runs from 24vdc to 42vdc, running ampere is about2.6A. There will always be supply to the motor which it will keep on turning until there is a overload (ampere increases) and its stop (holding ampere will be less than 1 ampere) with supply still on. Thank you.
 

Papabravo

Well-Known Member
Not enough information. What kind of a motor? Details? We're not mind readers.
 

wongkongwai

New Member
Thanks for your reply. I am so sorry, its the first time i join this forum. This is a tubular motor use for smoke or fire curtains. Need to design this for fail safe system, which means the curtain motor will always have supply (rolled up), when no supply, it will descend due to gravity.
 

crutschow

Well-Known Member
Most Helpful Member
How will the circuit be reset after the overload? Will the power simply be turned off?
 

wongkongwai

New Member
Hi,

There will still be power supply to the motor, to reset the power needs to turn off. Example on normal condition, the curtain is being rolled up and stop at the ceiling when the bottom bar(which is connected to the curtain) is "stuck" at the ceiling, causing an overload to stop the motor from turning further. There will still be supply there but when there is a fire alarm, the power supply is cut off and the curtain descend due to gravity of the bottom bars weight.
 

crutschow

Well-Known Member
Most Helpful Member
You could use a foldback current limit circuit such as EDN PDF. The will allow the normal 2.5A to pass, but when the overload you can design it to drop back to the desired 1A. The problem is that the limiting transistor may have to dissipate 30W or more continuously in this mode, so will need a good heat sink.

To minimize power, you could have a circuit that goes into a PWM mode to limit, but that would require a significantly more complex circuit.
 
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