X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com Message-ID: <539118CC.1040406@buffalo.edu> Date: Thu, 05 Jun 2014 21:26:36 -0400 From: "Stephen R. Besch" User-Agent: Mozilla/5.0 (X11; Linux i686; rv:24.0) Gecko/20100101 Thunderbird/24.2.0 MIME-Version: 1.0 To: geda-user AT delorie DOT com Subject: Re: [geda-user] Seized gear motor ~ steering questions and advice References: In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-PM-EL-Spam-Prob: X: 10% Reply-To: geda-user AT delorie DOT com Rob, By siezed I assume you mean that applying 12V directly no longer operates the motor. Two things come to mind and one depends upon whether the motor is brushless or not. If the motor is brushless then it must have an internal switching circuit for commutation. Such an electronic commutator is possibly incompatible with a PWM style driver and may have been destroyed - appearing to sieze the motor. Especially if it failed shorted - remember shorting a DC motor will cause it to act as a Brake. On the other hand, a brush commutated motor should have no problem with a PWM driver. The second possibility has to do with the motor itself - this would be a strictly mechanical problem. Once or twice I have had the stator magnets come loose on a DC motor - obviously causing siezure. Nevertheless, I can't connect the dots between the PWM and the magnets coming loose. Obviously, a gear could be broken as well, but I would bet against that. In the end, you may have to open the motor case to discover the problem. If it's a brushless motor my bet goes with smoked electronics in the motor. Stephen R. Besch On 06/05/2014 06:39 PM, Rob Butts wrote: > I got a cheap 12V gear motor from ebay and was using it to turn the shaft > of a trolling motor. The control circuit for it is a pwm controlled 3amp 8 > pin motor driver. With the trolling motor on a stand I simply applied 12V > from a battery to the gear motor to ensure that it would in fact turn the > trolling motor shaft. This worked fine in either direction. I have a > photointerrupter mounted adjacent to the shaft to keep track of turning and > direction. > > I then tried powering the gear motor via the motor driver circuit. I set > the pwm to about 30% duty cycle and set it to power the gear motor for 100 > ms. I could hear a brief sound. I then changed the pwm to 80% duty cycle > and changed it to 500 ms. There wasn't really a sound and now the gear > motor is seized. > > Any thoughts to why it seized? To be honest I have no idea if the gear > motor is brushless or brushed. > > After reading a tech note from Allegro I think I should be using a stepper > motor. I have no experience with stepper motors. Is this a better way? > It seems like I would have more control of direction (steps the motor > turns). > > Thanks!!! > -- fictio cedit veritati