240V 10A Motor Speed Controller - Page 1
Forum section: electronics / beginners

author: daniel444
author_rank: Regular Contributor
timestamp: March 31, 2020, 06:11:31 am
content: im thinking of buying this motor speed controller kithttps://www.jaycar.com.au/240v-10a-motor-speed-controller-kit-with-soft-start/p/KC5526my question is: can i use it for resistive loads aswell , like a heating element , assuming i de-rate it to 1500Watts ?anyone have experience with this kit?ill probably still buy even if it cant be used on resistive loads as it looks quite useful.thanks

author: beanflying
author_rank: Super Contributor
timestamp: March 31, 2020, 07:12:25 am
content: Speed control on single phase motors can be a bit of a hit and miss affair. That kit is also fairly expensive if you want to control a heater element of some sort and will tend to generate a fair bit of heat if you want to run it for extended periods.Do you require temperature control? What are you heating or cooking?If so a better approach would be to look at either a commercial PID controller and an SSR to suit your load or replace the PID with a separate micro controller which could give you more functionality if needed.This sort of arrangement is used in Wort heaters for Brewing

author: daniel444
author_rank: Regular Contributor
timestamp: March 31, 2020, 07:32:17 am
content: thanksyes i have experience with pid controllers, and own a triac based dimmer used for controlling brushed motors and heating elementsim interested in the kit because it puts out 980hz DC pwm i believe , and it claims will preform better on motors than a triac type dimmeri just want to know if it will also be ok on resistive loads as i have many different loads i want to use it on.it was featured in silicon chip magazine 2014

author: T3sl4co1l
author_rank: Super Contributor
timestamp: March 31, 2020, 11:08:11 am
content: Probably.Anyone's guess without a schematic. (Website is down at the moment. Oh neat, they have a crude Arkanoid game on their maint page.)Tim

author: Zero999
author_rank: Super Contributor
timestamp: March 31, 2020, 11:25:46 am
content: I don't see why it won't work with a resistive load. It's theoretically easier to control a resistive load, than an inductive load, such as a motor.I'd say it's overkill if all you want to do is control the output power of a heater, just use phase control instead.

author: Jwillis
author_rank: Super Contributor
timestamp: April 01, 2020, 05:19:24 am
content: From what I've seen The PWM AC motor controller is a Phase controller. Basically theirs a PWM that drives a optotriac that triggers the motor drive Triac or SCR. Instead of using the AC to trigger the thyristor in a rheostat phase controller. This can be used in single phase , 2 phase or 3 phase with a single PWM signal.

author: Zero999
author_rank: Super Contributor
timestamp: April 01, 2020, 11:05:17 am
content: Quote from: Jwillis on April 01, 2020, 05:19:24 amPWM and phase control are different.Phase control delaying the TRIAC so it switches on later on in the sine wave, thus reducing the RMS voltage delivered to the load.AC PWM or burst control as it's more often called, uses zero crossing and the TRIAC is turned on for a longer period of time, allowing several cycles to pass through to the load. It works at much lower frequency than the mains and is only used for heating.PWM is also used in variable frequency drives, but those don't use TRIACs. The incoming mains is rectified to DC, which is then converted to three phase PWM AC using MOSFETs or IGBTs.

author: Jwillis
author_rank: Super Contributor
timestamp: April 01, 2020, 08:00:01 pm
content: I understand that PWM is different from phase control. The PWMs Duty Cycle is used to trigger an optoDIAC which triggers a TRIAC. The MOC3021https://components101.com/sites/default/files/component_datasheet/MOC3021%20datasheet.pdfor similar Opto-isolator with Zero-Crossing Triac Driver is commonly used for PWM phase control of AC motors. Theirs no PWM burst .

author: Zero999
author_rank: Super Contributor
timestamp: April 01, 2020, 09:07:39 pm
content: Quote from: Jwillis on April 01, 2020, 08:00:01 pmI don't know what you're talking about. Can you please post a schematic or some waveforms?

author: Siwastaja
author_rank: Super Contributor
timestamp: April 02, 2020, 10:14:20 am
content: This is just a guess, but reading the specs, the product in the OP is most likely a decent brushed DC motor controller, so it would rectify the mains, then use a half bridge (likely a MOSFET or IGBT, plus a freewheeling diode) with current sensing and pulse-by-pulse current limiting and PWM to chop the power to the brushed DC motor; which is exactly what a "universal" motor is. This gives excellent torque and speed control and efficiency.I see no reason why it couldn't be abused to drive heating elements, given that their cold resistance isn't too low. With too little inductance, the pulse-by-pulse current limit won't work, so it can't save itself (the MOSFET/IGBT) from overcurrent if that ever happens.Of course, it's more complex and expensive than it needs to be.

author: Jwillis
author_rank: Super Contributor
timestamp: April 04, 2020, 10:27:14 pm
content: Quote from: Zero999 on April 01, 2020, 09:07:39 pmRead the data sheet. The schematic is there. Here's a one from ON Semi that explains it further.https://www.onsemi.com/pub/Collateral/MOC3163M-D.pdfIn the diagram it shows a NAND gate to signal the coupler . But provided the the forward current isn't exceeded a PWM will drive the optocoupler.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2020, 09:03:21 am
content: Quote from: Jwillis on April 04, 2020, 10:27:14 pmYes, I'm very familiar with those parts. They are TRIAC driver opto-couplers. The zero crossing one (e.g. MOC3062M) can only be used for on/off operation, so PWM at a low frequency, far below what's suitable for controlling the speed of a motor (hence completely unsuitable for this application) and the random phase one (e.g. MOC3022) can be used for phase control, or PWM at too lower frequency for a motor.To control the speed of a motor using a TRIAC, phase control, rather than PWM is required, so only the random phase opto-coupler will work. The MCU, or whatever is controlling it, needs to know when the mains is at its zero crossing point, so a transformer or another opto-coupler is required. Just PWMing the opto-coupler will not result in phase control. A short pulse is required to trigger the opto-TRIAC, a specified time after the mains has passed through zero, to control the point in the mains cycle when it fires.

author: Circlotron
author_rank: Super Contributor
timestamp: April 05, 2020, 11:04:48 am
content: The basic guts of the controller in question.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2020, 11:59:44 am
content: Quote from: Circlotron on April 05, 2020, 11:04:48 amThat's pretty much as Siwastaja described in his previous post and I expected. The motor is run off unfiltered DC, PMWed with an IGBT. It will work with a resistive load, such as a heater, but I don't see how it's any better than phase control, for a resistive load. It's certainly better than phase control for universal motors, but it's wasted on a heater. Also note that because it uses DC, it will fry some loads such as shaded pole motors.I've toyed with the idea of building a similar circuit myself, to control a vacuum cleaner motor, used in a balloon inflater which is too fast and tends to burst balloons, but will probably skip the MCU, as I don't need feedback. I've tried using a phase controller, but it wasn't very good.

author: Siwastaja
author_rank: Super Contributor
timestamp: April 05, 2020, 12:08:24 pm
content: Quote from: Zero999 on April 05, 2020, 11:59:44 amVacuum cleaner motors runbeautifullyfrom a DC supply. A 230V vacuum cleaner starts to produce some noticeable vacuum at about 50VDC.