Trouble Wiring Up My First Motor - Page 1
Forum section: electronics / beginners

author: electromateria
author_rank: Regular Contributor
timestamp: October 20, 2020, 05:00:55 am
content: Hello everyone,I'm trying to wire up a motor and am having problems reading the schematic. I watched about 5 youtube videos explaining how to read them but I'm confused:I have lots of questions...Where does this diagram start? With the red wire to the far left?Why isn't there a motor icon with all the wires branching out as a start point?Inductors are required? ugh oh. I don't have them anymore. What are "M", "A"?There are two red wires I don't know the difference.What is that symbol that looks like an open switch with an extra symbol on top?Can I use a potentiometer (or something better) to easily vary the speed?I saw in a youtube video resistance can be tested on each wire to find which ones control the corresponding speed winding. Do I need to do that?Sorry about so many questions, I don't know almost anything about electronics, I'm just starting out and I'm very confused haha...Cheers

author: helius
author_rank: Super Contributor
timestamp: October 20, 2020, 06:33:17 am
content: "Single phase asynchronous" is a less common way to describe aninduction motor. The type in the picture is a run-capacitor, split-phase motor.Quote from: electromateria on October 20, 2020, 05:00:55 amThe diagram only shows a motor, so it doesn't really "start" anywhere. Normally power enters on the black and white wires; this is shown by the ~ symbol for AC. Black and white are standard colors for Live and Neutral in North America.QuoteA simpler device such as a DC motor can be described with a "M in circle" symbol. This device is more complex.QuoteNo. The "inductors" in the diagram are the motor stator windings. These motors have a Main and Auxiliary winding, the Auxiliary is used for increased starting torque.QuoteSince they are used to connect the (non-polarized) run capacitor, they are interchangeable for this use.QuoteA thermal cutout or fuse. They are normally a small metal cylinder with axial leads.QuoteTo have varying speed it would be easier to use a DC motor with a rheostat. This induction motor turns at 1800 rpm idle and less under load.The formula for induction motor speed is \$ RPM = 120 \cdot \frac{f_AC n_poles} \$You can alter the speed by changing the phase between the Main and Auxiliary windings, by changing the capacitance attached to the colored wires. Variable capacitors are usually implemented using electronic circuits.QuoteThe windings are already depicted on the diagram.

author: Nusa
author_rank: Super Contributor
timestamp: October 20, 2020, 07:24:27 am
content: Someone else playing with the same motor:https://electronics.stackexchange.com/questions/454512/wiring-asynchronous-motor-with-terminal-in-middle-of-aux-windingAre you putting the dehumidifier back together, control board and all? Or just playing with parts?

author: electromateria
author_rank: Regular Contributor
timestamp: October 20, 2020, 07:44:24 am
content: Quote from: helius on October 20, 2020, 06:33:17 amThanks for the detailed responseThe picture is becoming clearer!I'll leave out the auxiliary winding and any kind of speed control for now if possible. It sounds too complex for my level.I heard a momentary switch can be used for the capacitor? A guy in youtube comments said if the capacitor gets power continuously during operation it will burn out, it's only meant to kickstart the motor then turn off. Is a momentary switch a good solution? If so any tips on how I would wire it up?Is this wiring correct?I'm not sure if I'm allowed to ground on the capacitor bracket (probably not lol!). The fan has an all plastic casing, should I drill a piece of steel onto the side and put the ground on there instead?Quote from: Nusa on October 20, 2020, 07:24:27 amI'm using the fan as a forge blower. No more control board, it's sitting outside in the rain waiting for trash day (I probably should have saved it).In that link they mention abnormal draw / run speedhmm. Any (simple) way to counteract this or make sure I don't fry everything?

author: Nusa
author_rank: Super Contributor
timestamp: October 20, 2020, 09:27:54 am
content: That's a run capacitor, meant to be in the circuit all the time. There is no start capacitor or centrifugal switch, which means it's weak on starting torque...but that's ok for a blower-type load, since air resistance only happens when it gets moving.See what you get when you try it. Your experience may be different. That post also seemed to think his motor might have a damaged coil.As for the safety ground wire, there should be no continuity between that capacitor case and the terminals, so should be fine. (Make sure the cap is discharged first if you actually test that.)If it's a thermal fuse, it should be physically attached to the motor case in some manner.

author: Ground_Loop
author_rank: Frequent Contributor
timestamp: October 21, 2020, 03:27:08 am
content: Connect power neutral to the black wire and power hot to one of the red wires and it should run. If you then connect power hot to the other red wire it will reverse rotation. Cap off the white, unused red and yellow wires.

author: electromateria
author_rank: Regular Contributor
timestamp: October 21, 2020, 10:11:42 am
content: Quote from: Nusa on October 20, 2020, 09:27:54 amAh perfect, that makes sense regarding the capacitor.I wired it all up (I left out the fuse though). The motor started right up and really puts out a very strong blast of air! Should I test how much power it's drawing to make sure everything is ok?I have some on/off switches and I want to add one, but they all have different power ratings. Some of them are listed only for DC. Can I just throw a switch into my circuit or do I need to potentially add a resistor? Any tips on choosing the right switch?The capacitor and wiring are covered by a plastic grill (quite exposed). Do they sell covers in electronic shops to keep components away from dust and water spills?I took a video of the blower running so you can check it out:https://streamable.com/2r6a9i

author: Gyro
author_rank: Super Contributor
timestamp: October 21, 2020, 10:36:08 am
content: Quote from: electromateria on October 21, 2020, 10:11:42 amI just noticed that the motor label specifies a 6uF run capacitor and you appear to be using a 15uF one. That probably means that the motor isn't running optimally. Best to replace it with the specified value - this won't affect the running speed or output power, but it will draw less current and potentially be quieter.Motor run capacitors are cheaply and easily available and as a bonus, a 6uF one will be physically smaller and easier to fit in.As far as protection, insulated crimps and heatshrink sleeving are probably best for avoiding accidental contact (probably won't help with actual spills though) and neatly bundle and secure the wiring using cable ties.

author: Nusa
author_rank: Super Contributor
timestamp: October 21, 2020, 12:29:53 pm
content: Quote from: electromateria on October 21, 2020, 10:11:42 amIt's not real clear from the diagram, but the thermal fuse might already be part of the motor package. So long as the motor isn't getting too hot to touch after a few minutes of operation, you're probably good to use it.Pick a switch that actually lists an appropriate AC rating. Save your DC-only rated switches for DC projects.If it were me, I'd use a surface mount metal electrical box, standard light switch (15A 120V AC typical) and cover plate. Wire up the hot lead through the switch. I've got all that on hand, but probably less than $5 at the hardware store even in Canadian loonies. If well placed with a hole drilled through the side behind the box, you could probably pull most of those wire connections into the box as well.

author: electromateria
author_rank: Regular Contributor
timestamp: October 21, 2020, 06:50:25 pm
content: Quote from: Gyro on October 21, 2020, 10:36:08 amStrange, that's the exact capacitor that was originally used with the motor.I'm going to the electronics store later today I'll see if I can find a 6uF one. Thanks for the heads up!Quote from: Nusa on October 21, 2020, 12:29:53 pmOk that clears it up, thanks for your help! I'll post a few pictures of the blower once its finished.