Rectifier / solid state relay speed control?

Still haven’t got speed control, I have been looking into all sorts of speed controls. Now I came across full bridge rectifiers, which are some what cheap. From my understanding it just changes ac to dc. But the dc that comes out gets a ripple effect, which I read and can be cleaned up with capacitor multiplayer circuit (widely used in higher end audio systems). Then I can pwm or dac the dc signal. I’ve read extensively that the universal motor will run the same on dc with same power input. So the idea is:

Rectify 120vac 15amp (whatever is coming out of my wall plug) to dc …ends up being 127vdc . After filtering and hardware loss should come closer to 120vdc still maintaining the 15 amps maybe some loss on amps… didn’t read anything on amp loss

From my understanding running a universal motor with no load on ac will just keep accelerating until max Input power , if resistance is not added on the input circuit. Which I opened mine Apart yesterday and saw it’s just a cable to a switch to the motor. I am assuming this is why the rating was 1200w , I am assuming they just multiplied 120v * 10amps to get the 1200w rating. The only thing that might give the motor any load or resistance control is the exhaust fan which is connected to the shaft.

Now, after rectifying the ac - dc you can invert it back to ac ( this is how vfd work) I have one of those car inverters it is rated 400w / 800w peak. Don’t know if that is the type of inverter That I can use since it’s meant to run off 12v and has alot of amps to work with. I read it’s some sort of IGBT inverter that you need, another project for another time.

Solid state relay. Basically from my understanding is opto controlled circuit that is controlled with a triac , so no mechanical latching all digital, the gate of the triac is working with its internals to do zero crossing etc, I had a random idea of by passing the zero cross detector on the relay with pwm or dac signal that is controlled by programed MCU with the rpm sensor. I don’t even know if that will be a viable alternative then having to pair / solder components for 120v 15amp circuit to get the full ac load which can produce much higher then The PIDs for sale that are 500w rated.

So any advice on converting ac to dc with rectifier to use dc style speed control, or do you think it is possible to bypass triac gate on SSR?

Something like this works with the dw660, and most “dumb” motors. It is just a triac inside, where it will stomp on some percentage of the AC cycle. It isn’t synced with the start or anything, but it works fine. The only trouble is, it isn’t controlled by software.

If your goal is to control it by software, then you can also get triac control, and it will be pretty simple. Ryan sells a triac and a nano. There is some code (and for some reason has been really popular recently). The triac can only control the amount of power going into the router. If the bit hits resistance, and the power isn’t adjusted, it will slow down. The PID part is adding a sensor into the router, and when it gets slower, increase the power (up to straight wall power 120VAC).

You can skip to the last few posts to see people working on it right now:

Your idea of converting to DC with a rectifier, and then using a SSR to clamp the signal to achieve PWM is good. I’m not sure if you need to go back to AC at that point. I would be pretty shocked if your DC inverter would work in that situation. Those care inverters have components selected to get power from a 9-15V DC power source, invert it (15VAC), transform it (up to 120VAC), and power small stuff in the car.

The other thing I would point out that is wrong above is that the wall power is a constant voltage power source, and in the simplest model V=IR. So the amount of current that gets drawn from the wall is determined not by the wall’s max current rating, but by the electrical resistance of the load (the motor). The DW660 is 600W. Power is voltage times current, so ignoring all the details of RMS, and AC/DC, that means it would allow 5A to flow at 120V. So the electrical resistance must be about (again, just a big fat estimate) 120V/5A = 24 Ohms. That includes “real” resistance, like the wires, and impedance, which is from the coil getting harder to move as it goes faster. If you rectified the 120VAC into 120VDC, and sent that through the motor. I think it would still have about the same resistance, and would still draw about 5A from the wall. If you were clamping 50% of that, it would be taking 5A sometimes and 0A when it was off, and average about 2.5A. If I were to guess where the biggest mistake in this estimate is, I would say that the resistance of the motor may change when you power it by DC. The impedance may not be as high with an AC signal. But that’s outside my understanding, really.

You can think of power as water. Pressure is like voltage. A valve is like resistance. The amount of water is like current. If you have a hose from the side of your house, the amount of water isn’t constant, but the pressure is. If you open the valve a little, you get a little water. If you open the valve a lot, you get a lot of water.

IMHO, power electronics is pretty complicated, and although it is very interesting, I would suggest staying away from making your own kit. The PID kit is probably along the lines of what you’re looking for, but be careful. 120VAC can hurt or kill you.

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Thanks for the info, I have read most of that thread as of maybe 1 week ago. That’s where I got one part of the idea for using the ssr the same way as the triac is being used in the PID. it just has all the components for whatever voltage rating already in a nice ul approved package( as if I cared) then just doing the same thing as the PID project and connect to the gate of the onboard triac in the ssr. I would buy it, I was going to, but that max 500w rating is still troubling me since the “rated”output of my router is 1200w. I’m sure it’s not actually 1200W… but even at half is more then 500w.

I installed converted my old circuit shot gun plug style circuit breaker at my house, and one day my mains got severed from this house being next to salt water and metal pipes from the 50s, I re attached my mains to the meter… I’m not well versed how it works as much as actually working with high voltage.

Jeez, I went from a quarantine diy project to make my kitchen cabinets and 3d printing hobby to trying to EE, with my experience more like rig, solid state relays and make vfd Power supplies… :grimacing:

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Also, I did do a lot of research on that motor controller seeing as there is a Harbour freight around the corner from me. I saw a video of a guy ripping it apart, and it actually has another POTin the back to adjust it even more, but it’s all the same concept of tapping into that triac with an octocoupler of some sort to separate the mcu from the mains. In that case is the same as the case of the ssr concept I had… just found this ,thisguys going down the same road I am. Seems he has a simple solution… already got 4 rectifiers on the way :grimacing: from amazon, Ordering the caps for filtering shortly. Either way I will use them for the work bench power supply I want to make…

One thing to watch out for is a motor is an inductive load which means it really doesn’t like being switched on and off quickly. Like Jeff was comparing to water, switching off quickly can produce “water hammer” voltage spikes, and when switching on, it takes a little time for the current to start flowing. This means starting with a DC power supply and applying PWM is not likely to lead to good results.

A triac like in the cheap dimmer switches have a nice way of dealing with inductive loads. When the AC voltage rises on each cycle, they delay turning on, so the power is only provided for a portion of the cycle. When the AC voltage goes back down and the current reverses, the triac shuts off when the current is zero. Since the current has “momentum” (from the inductance of the load) the voltage and current do not reach zero at the same time, and by switching based on the current being zero, no voltage spike is produced. This is gentle on the triac and allows it to be cheaper. There is a difference between SSRs made for DC and AC loads. SSRs for DC are more expensive because they have to switch off a load while it is on, while the SSRs for AC will wait for the current to be zero to switch off.

Also, about running tools with no load, as they run faster, they produce reverse voltage like a generator. They won’t run away until they are burning a full 1200 W (or whatever). As the speed increases, the reverse voltage from the generator cancels some of the voltage from the wall and the amount of current decreases as a result. There is also resistance converting electricity into heat and air resistance providing friction on the tool but these are not absorbing 1200W of power. The tool is consuming less power when it is not under load.

I think your best bet is an AC dimmer switch or Harbor Freight equivalent, and I think those can be more intelligent in the control based on feedback. But trying to go to DC and SSR and PWM is going to be a problem.

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:thinking: at the moment, I can’t actually think clearly , will have to read over this tomorrow. Thank you for the info, that being said, I will look closely into it. I just figure , at this moment, couldn’t the system just keep on losing vdc… I have around 50 vdc to burn( I’m not trying to make the perfect machine or anything), but I think with 50vdc I have a lot of wiggle room. Any components that I can add to the circuit, including cooling should be within reason, while allowing the system to have ample Vdc to run Without breaking 20a ac., I got an open 240, and full control of both legs of the mains from the meter back… I could go further but that’s not what I’m aiming for… I want to keep this 120v 15 amp ac - to dc , I’ll have same Amp and v to burn I think… (if “rated motor is 1200w ac at 60hz”) then I Think (sometimes) i only require 10amps for the motor, how that translates to dc, no clue. I figure I might as well burn the v through actually powering something , vs. Creating a lot of heat on one component. As far as the speed control, why would it be hindered by Pwm on dc , I also mentioned using dac, which I believe is i2c which would alot for variation on or from 8 bit to 8^2 .

The reasoning behind this bit mapping , is that including the esp32 port project . Is to leave 8 bits to whatever controller you have . My case the cnc shield v3 which uses the Arduino uno. An 8 bit system stand alone . But for efficient data transfer to that 8 bit system . You need to keep … dedicate 8 bits to maintain constant data flow rx tx without interruption from the system I am trying to realize . Using the same esp3d that I use with my esp32 cam github program that I didn’t have to solider anything into because my ender had a USB port, and utilizing dat± I cjust connect the cable instead of soldering . I thank the people who created that . Because it is the basis to this… i plan to not keep anything from anyone .

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Jeez hair of the dog Situation at the moment… don’t know why I do that to myself…
Again, thank you for the information I’m going through it now. Normally I just make things and never post nothing on forums. But in this case I am dealing with high v vs. my usual projects which are under 12v (car/boat… Arduino style) that and since a lot of time has been spent on this community to have this resource is great. I thank everyone again for help/guiding me to the right solution based on there experiences.

Hmm I see, the ssr and rectifier wouldn’t have been used together, my fault in not articulating that. It would either be trying to tap into the ssr triac on an ac - ac situation not ac-dc. The rectifier would just be ac-dc then modulate power using a buck convert / scr type set up to manipulate the dc , as is done in any dc style motor control.

Let’s see what happens…

I’m a have to get a neighbor or something to make sure I don’t fizzle…

Come think about it where the f is my wife …totally forgot about that individual… been like 3 months :confused: bank account is about right … back to plugging this in

Yay, more parts , waiting on caps… then darlington transistors once I get new values :grimacing:

And some 4x4 for legs of this thing… someone was throwing out these bad boys…

And I got my 1970 Yamaha cr1000 back… 90 watts studio amp… 90 watts per channel this house is gonna be my power companies best consumer of the year :joy:

Is that your living room?

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Lol yeah… haha I been busy / raining outside haven’t been able to work on it. It’s gona go in my kitchen area… which is 5ft away lol. I’m in the process of re doing my kitchen / living room area so it’s a disaster in here as it is. But once I finish the kitchen then I’m going to dismantle it, shorten the tubes, or just slide them through and use the wood from that frame and level up my bar/counter in the backyard and print some sort of those belt clamps. I dunno if it’s my stubby fingers or what but putting those little spacer zip ties took me like an hour…

But got my capacitors in, the rectifiers, cable plugs, I had taken apart acouple cd Roms before I made this to build one of those cd rom cnc machines out of boredom when this whole pandemic started… except 4 out of the 5 used regular dc motors with a Hall effect sensor and gears… I looked at all the chips and one of them actually had a 6ch driver. I think all this stuff will fit one of them cases, add some modification to add some fans, and make sure it’s properly grounded.

Got to figure out my triac, regular thyristor,bjt, or power mosfet delema. I think I’ve read to many data sheets that It’s all one big jumble in my head, taking a day or two to focus on making / tinkering with microscope , with pi cam and one of them lens from the cd rpm drive. Saw someone did it. And I’m waiting on this darn drain cleaner to get here to finish my little foundry I’m making. Sooner then later got a trash bag full of cans… gona melt them down and into some heat sinks for this power supplies I’m building. Projects…

Ha. Now I got to cad up a little lens holder/ focus ring, to sit inside the cams manual focus thingy…

I been messing with the cam modules, the pi one is half way decent , but the one I am planning on working into my router holder/ vac boot design. I know the esp32 cam has face detection and can track x y of the cams viewing area… trying to see if I put like a certain color sticker or something at my
x y starting point , that it can figure out where it has to move to get to the dot. Kind of like line tracking. And then have it offset so the bit lines up to the mark.

Got a little mock up going figuring out the space I got, might make a simple pcb for this , got to figure out that egale program or something. But I think I’ll be able to hard wire this…

*Looking at H bridge circuits now… tough to find in the 120v range. So far what I understand of the triac I need to get is closed loop so I can control the zero crossing… But what I am trying to understand about that being useful is that… the rpm sensor would be controlled by the mcu, which if programed properly will calculate the the amount of voltage change necessary to adjust for when it goes on and off load, or when changed through gcode , by changing the pwm which is connected to the gate. Depending on the feq of the pwm it will open and close the circuit however it’s told. So then these gate drivers that go on before the triac are in the case that, the triacs gate is not rated to logic level voltage. At that point I can get rid of the driver, and to isolate I can use an optocoupler to connect the pwm output to the gate. Or is the driver have another purpose like voltage feedback, so that the mcu knows how much voltage is actually going out, so that then it can calculate the rpm to the voltage ?

Rough mock up to help me visualize the design of the face plate and what I need to cut off the case. Got one of those 15a fused sockets in the mail. That I will replace the breaker, and the socket that’s sticking up out the back.

Ooo and my fpga came in today… that’s for another time… hopefully can get that thing to take away all of this issues. and program it to be all the motor drivers and it has a 32bit soc on it too with WiFi. That’s for when I figure this out in a physical state. That’s why this thyristor issue is important, 150mhz pin output per pin . So that should would be very high resolution on the pwm signal.

People like you make me sick…

with envy!

Electrics and electronics go by like subtle metaphors past Drax. I know enough to not burn the house down when changing switches or light fixtures, but that’s about my limit. I can do computers better than average (if nothing else, because I’ve been doing it all my life), but circuits are so far out of my ability to visualize, especially analog circuits. I much prefer simple state machine mechanics…

I hear ya. That’s about my level. Time to explore beyond since I got the time at the moment. This is actually the first part to a much bigger project. If I can get this part done , then I can move onto making my bench powersupply, that I want to have it run like an oscilloscope/ multimeter all headless. Pulled apart an old cable box and got a ac-dc power supply out of it 25vdc already has 12v 6.6v and 5v pins. It’s in that picture too. Going to start small first on that project.
You’d be surprised of the stuff you can pull off already working junk in the attic… and just print / cnc a case for it