I need to build a simple, cheap control circuit for a 12v DC motor operating from a 12v DC power source, and I have most of it designed, but I have run into a problem.......
I need a way to sense that the motor has stalled so I can cut off power to it.
I have no idea how to do this, or where to look for help, or even what such a circuit is commonly called.
There is no practical way to add a seperate tachometer or position switches.
In case you are interested in more details and why I need this.......
I am building a mechanical device for use in a show car. The device extends and retracts body panels to change from a maximum ground effect setting to a setting for "real roads" where the ground effects are retracted. There are only two desired states which I refer to as "extended" and "retracted". I have no interest in being able to stop the system part-way between states, or vary the speed of the system.
I have the mechanical parts of the system working and am using a spare power window motor to drive it. The motor I am using has two wires and rotates forward when power is applied in one polarity and reverse in the other polarity.
The current draw of the motor is high at startup (20a) and during the first half second or so of operation, but drops (6a) and does not vary significantly during the 4 seconds it takes the system to operate until it goes up again (35A) almost instantly when the mechanism hits the stop or jams.
The motor can withstand a stalled condition for several seconds without overheating just as it would do if you held a power window button in the Up position when the window was closed. In the normal use a 30A delayed acting, self-resetting, circuit breaker opens if you do this. I was hoping for something more elegant and less hard on the motor since this condition will occur everytime the system is switched from one position to the other, as opposed to the window application where this is considered a once-in-while failure condition.
My design for the system followed the usual way power windows work--- the mechanical system has stops built-in at both ends of the travel, but I did not build a switch into the system to sense when the panels were fully retracted or fully extended. I assumed I could easily find a circuit to detect end-of-travel by motor stall and I also wanted the system to stop if it jammed or hit an object laying under the vehicle also causing a stall. It does not need to automatically reverse when it hits a jam- just stop.
I don't really need to be able to differentiate between the motor startup current and the stall current, as I can easily ignore the stall indication signal during the first 1/2 second or so of operation.
Any designs, suggestions, or even keywords to search for will be greatly appreciated.
Thanks In Advance, Ben
I need a way to sense that the motor has stalled so I can cut off power to it.
I have no idea how to do this, or where to look for help, or even what such a circuit is commonly called.
There is no practical way to add a seperate tachometer or position switches.
In case you are interested in more details and why I need this.......
I am building a mechanical device for use in a show car. The device extends and retracts body panels to change from a maximum ground effect setting to a setting for "real roads" where the ground effects are retracted. There are only two desired states which I refer to as "extended" and "retracted". I have no interest in being able to stop the system part-way between states, or vary the speed of the system.
I have the mechanical parts of the system working and am using a spare power window motor to drive it. The motor I am using has two wires and rotates forward when power is applied in one polarity and reverse in the other polarity.
The current draw of the motor is high at startup (20a) and during the first half second or so of operation, but drops (6a) and does not vary significantly during the 4 seconds it takes the system to operate until it goes up again (35A) almost instantly when the mechanism hits the stop or jams.
The motor can withstand a stalled condition for several seconds without overheating just as it would do if you held a power window button in the Up position when the window was closed. In the normal use a 30A delayed acting, self-resetting, circuit breaker opens if you do this. I was hoping for something more elegant and less hard on the motor since this condition will occur everytime the system is switched from one position to the other, as opposed to the window application where this is considered a once-in-while failure condition.
My design for the system followed the usual way power windows work--- the mechanical system has stops built-in at both ends of the travel, but I did not build a switch into the system to sense when the panels were fully retracted or fully extended. I assumed I could easily find a circuit to detect end-of-travel by motor stall and I also wanted the system to stop if it jammed or hit an object laying under the vehicle also causing a stall. It does not need to automatically reverse when it hits a jam- just stop.
I don't really need to be able to differentiate between the motor startup current and the stall current, as I can easily ignore the stall indication signal during the first 1/2 second or so of operation.
Any designs, suggestions, or even keywords to search for will be greatly appreciated.
Thanks In Advance, Ben