Reliable DC Motor controllers - Page 1
Forum section: electronics / projects

author: pratiken
author_rank: Contributor
timestamp: February 13, 2016, 04:57:53 am
content: Hi everyoneI'm designing an apparatus that's going to slowly rotate a small 10" turntable with very little weight (~2 LB) over long periods of time. Let's say, 1 RPM for 7 days straight. I'm using a worm gear setup with a planetary gear motor rated at 2,124 oz-in. (12VDC) with Max No-Load Current: 0.53A. I realize this might be overkill for this application.I'm using an arduino to run this setup. With that, will any L298N based motor controller work for this? What goes into the reliability factor for motor controllers? I don't want this to die on me in 2 years.A key factor is that I need it to fit into a small space. I have about 65mm*55mm and height: 40mm of space to fit the driver in.Thanks for your advice!Pratikenedit: I did try searching. There doesn't seem to be a lot on the topic of motor controllers and reliability. I suspect for industrial applications, proprietary controller boards are assembled, no?

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 13, 2016, 05:28:52 am
content: Just make your own driver using a power MOSFET. Use parts rated for well above what your application needs (even high current MOSFETs and Schottky diodes are cheap) and it will last a very long time.

author: Ian.M
author_rank: Super Contributor
timestamp: February 13, 2016, 06:17:15 am
content: Most of the motor driver chips available are bipolar and either require heatsinking or tend to get warm at even moderate loads. A power MOSFET will have a low Rds_on, so will run cool at similar load currents, with improved reliability (assuming the driver is properly designed). You haven't stated whether the motor is reversible or if you require active braking, which determines whether you need a full H-bridge or can settle for a single low-side MOSFET and a freewheeling diode across the motor. Its worth adding a fast current sense circuit so the driver can shut down fast enough to save the MOSFET or H-bridge if the motor is jammed or shorted. Ideally you want the amplified current sense signal to go to a comparator input on the MCU that will shut down the MCU's PWM module in hardware if the threshold is exceeded. I don't know if that's easy or even possible in an Arduino, but it is absolutely essential to shut off the drive before the shortcircuit current pulse takes the MOSFET(s) outside their pulse SOA curve limits. Fuses wont save you here. Microchip make it easy with ECCP modules that support auto-shutdown in PWM mode, and can either do cycle by cycle current limiting automatically or trip off till the control program resets the module.

author: dom0
author_rank: Super Contributor
timestamp: February 13, 2016, 02:37:09 pm
content: It's not hard to that in hardware, but definitely requires a lot more parts than doing it in the MCU. If the MCU has an analog comparator but no hardware, ideally even clock-independent, path to do the shut-off, just do it externally. Don't rely on an interrupt fired by a comparator to disable the PWM or something like that.

author: Paul Price
author_rank: Super Contributor
timestamp: February 13, 2016, 02:51:01 pm
content: Simplest, cheapest, reliable motor speed controller.https://www.eevblog.com/forum/beginners/artnoise-project/?action=dlattach;attach=200770;image

author: dom0
author_rank: Super Contributor
timestamp: February 13, 2016, 03:01:21 pm
content: Replace the motor with a short and watch M1 explode.

author: Paul Price
author_rank: Super Contributor
timestamp: February 13, 2016, 03:05:18 pm
content: It would not be good engineering practice to design-in or replace M1 as a short.