SMC3 based DIY 2DOF from NZ

So a week or two on and my Monstor Moto board has now arrived and things can progress again! I now have all of my hardware for the motion and i am in the process of sorting adequate wiring and connectors. I have a friend who owns/runs a car wreckers so I have gone to him for parts and I am a very lucky boy as wiper motors and driveshafts have cost me a box of beer. At this stage, I am not convinced the motors will be big enough but when starting out, I tell myself everything is a "proof of concept" and then once proven, I can and will invest in bigger, better motors.

I have got 2 x wiper motors from early 2000 Ford Mondeo's to start with. As a wrecker, he has said he has never sold one or known one to break so that's a positive. And I was given 2 x steel, wide diameter driveshafts (just in case) that I will be able to chop and make use of. Getting heavy steel ones will make welding and weight bearing a whole lot mentally pleasing.

Let the building begin! Nothing stopping me from building the frame and platform now. I am intending to build/find an enclosure for the two controller boards with a fan to keep things looking tidy so will salvage an old PC PSU, gut the case and re-wire the fan to run off a separate 5v power supply. Will put up a diagram of my intended plans shortly hopefully!

I know there are plenty of wiring diagrams out there but sometimes I need to see things in-front of me to make sure I understand what I am trying to do and achieve. It also helps me work out what hardware I need to purchase to make it all happen. This is a breakdown of what I am hoping to do including creating a "ignition" panel with all of the 5 missile flip switches.



If somebody can see any problems or troubles, please tell me sooner rather than letting me fall on my own sword as from my understanding, this should work.

Fuses!!! and lots of them

You want to at least put a fuse between your PSU and you MM, just in case, so you don't accidentally let out the magic pixie smoke, that smoke is really hard to get back in to the wires.

Also, depending where your missile switches are, I would consider using relays so you don't have to send the 12V all the way up to your switch panel. And especially the 240V stuff, there are real angry pixies in those 240V wires and you don't want to mix your high voltage and low voltage stuff in the same box.

You might want to look at a latching killswitch also.

For the PSU, are you switching the power on/off on the 12V side or the 240V side?

Right, fuses - I have taken that on board and shall try find an appropriate one to put between the PSU and the MM. I guess this is a just incase if the PSU outputs more than the required 12V?

The missile switch on the PSU is on the 12V side. It's a standard jug cord into the PSU and then I am putting the switch across the 12V jumpers for this particular HP server PSU. If the jumpers don't connect, the PSU doesn't turn on. So I'm not even convinced that it would be a 12V but I will test with a multimeter and find out what kind of current is going across those jumpers.

3 other missile switches are all 5v cooling fans on their own power supply so I wasn't going to bother with relays for them. And the 5th switch is just a relocation of an existing switch.

I did contemplate a kill switch but I thought the tactically placed missile switch on the server PSU would be as good as a kill switch.

Thanks for the feedback and suggestions!

Fuses work on current, not voltage. So they will blow if they go over a specified current. It is there to protect against a short in the controller box or in the board where in fails closed. In that case if you do get a short then it will just blow the fuse instead of blowing your PSU or melting the cables and starting a fire etc, you know, all the bad stuff.

You typically don't need one between the motors and the the MM because the MM has over current protection and it will just shut down if there is a short in the motors.

If it is just for the on/off jumper switch on the PSU then it usually pulling the pin low, i.e connects it to ground, most PSU's use 5V with a pull-up resistor. If it is just pulling it low then you don't need to worry about using a relay because there isn't any real current running across the wire.

Yeah, the 5V is fine without a relay, it was only if you were going to be taking the 12V all the way up to the front of the rig and all the way back down to the controller box that I would put a relay in.

The on/off jumpers would be the perfect spot to kill the rig, that kills power to everything.

So another night and more progression and learning. Not all stepping forward but definitely two steps forward and one back.

I have soldered and wired everything up to the point where I should be able to do a bench top test and make sure everything is working as it should. I have 80% of my "final product" wiring and connectors in place but the other 20% will depend on final layout and needing to buy more wire.

NOTE FOR BEGINNERS AND LEARNERS - make sure you follow this tutorial/suggestion/must do when starting out with wiper motors:

https://www.xsimulator.net/community/faq/wiper-motor-mandatory-ground-isolation.25/​

Luckily I wasn't silly/brave enough to wire everything up and plug it into the computer and go straight into config. I thought I would ground test my wiper motors "just in case" and it turns out both of my motors have the casing connected as negative/ground. This means my next step will be following this tutorial to the end and isolating before going any further.

Today's progress = not much...

I pulled open the wiper motors to find the particular brush that was connecting to the motor case, cut it and soldered a new wire from the brush to the ground. Not too much of an issue, seemed easy enough. Powered motor back up and what do you know, the casing is still connected to ground somewhere! I even put a splodge of hot clue over the existing case connection area so there was no way the new wire and connection point would touch. I don't really want to go and open the motors completely up at this stage so my intention is to mount the motors on nylon bushings and then to my frame. Yes i know people will probably boohoo this "easy way out" but at this stage, I still don't even know if these wiper motors will be enough to move everything sufficiently.

Also found that my server PSU is using its own metal case as a ground as well so I have brought a little plastic container to house the PSU and newly installed fuse (thanks @Avenga76 for the tip).

Frame plans have now been finalized and sourcing steel at the moment. Awaiting switches and more wire to arrive and once i have those two components, I should be able to finish all of the electrics.

What are your rods connecting the back of the frame to the motors going to be made of? I had a similar thought process in my build, thinking I would be in the clear because I had a wooden base so the motors wouldn't be in contact with each other, but they ended up getting connected through the rods and seat frame.

Post a picture of what you did on the inside of the motor, as well as any main wire connections going from the plug to the motor. Yours look almost identical to mine that I just did this to so it's fresh on my mind, I'm thinking it may be something easy you might have overlooked.

Not sure if this was what you actually intended to type? But the new wire that you have connected to the brush should go to 0V of the power supply or motor driver (depends on your configuration), not to ground. The casing of the motor is what should still be connecting to ground via a new wire. Hope that clarifies things?

You are correct, I described it wrong and wrote the wrong thing. I did connect the component to the 0V and not the ground first time around. I dont have anything coming from the motor casing ground point at the moment.

You make a good point here and since thinking I would do it this way, I am like you, I cannot think of a way to isolate the motors from the chassis because at there are metal screws connecting everything and I don't have any way of creating non-metal armature. Looks like I will have to sort the problem instead of trying to side step it.

Pictures attached below:

Here is an overview with the cover off


Here is the new wire from the component to the 0V/negative motor wire


Original copper braided wire was from red component to the case. Here is new wire connecting to red component


Here i am trying to show the location of where the copper braided wire was connected to the case. You can see it under the hot glue blob.

Also, sorry for the delay in responding to you @armpit and @RandomCoder, i REALLY appreciate your input and feedback and suggestions but I have been busy welcoming my 2nd child and 1st daughter into the world!

Congratulations, I hope that mother and daughter are both doing well. Family is a very special thing, and kids grow up far too fast! Take the time to enjoy them whilst they're young!!

Congrats on the kid!



My motor looks to be laid out almost identical to yours. I believe the "red component" in yours is an overcurrent protection chip like this smaller black/yellow one in mine. In my case, the bottom pin was connected to the case/ground on it, and I found that I could bypass the chip completely.

I'm not an electric motor expert, someone can feel free to chime in here, but I believe this component can be safely bypassed since we are using an external controller that has built-in protection.

There's a chance your red component is still connected to case/ground without you realizing it, you could try to take the braided copper lead off of the top and connect that directly to the negative coming from your motor controllers and see if you still have continuity with the case after that, my guess is you will be in the clear.



Also, if there's another way to run the wire into the motor housing that is less at risk of rubbing through the wire insulation causing a short against the case, you should try to do that.

I ran mine through a rubber block where the high/low speed wires came in

Progress on the motor ground isolation has been productive tonight but I have hit a wall. The electric component you speak of @armpit is a standalone part in my motor. I pulled the part out of the board and confirmed it wasn't in contact with the case but I still took it out of the circuit and soldered a wire straight to the brush.

I started point to point testing with a multimeter and found that my hurdle is the plastic moulded connection plug mechanism. The negative pin in the plug appears to be connected to the case within the plastic moulded housing. Probably sounds silly but there is nothing visual external of the plastic housing yet somehow the case is still connected.

This picture is of the inside of the motor plate and plastic housing.

I have found which of the pins (furtherest right copper terminal) is the negative compared to the plug wire but yea, something is still connecting the case within.

Not sure how to go about getting into the housing or what to do next but that can be for another night. I have found my issue and it turns out my motors have two case ground connections! Surprise!

Not only do you have the ground connection but also diodes built into the connector to prevent against reverse polarity! Good find, well done

I guess that helps me understand what the diodes are doing. So I'm guessing I will need to take those out of the circuit as well?

Yep, you sure will.

Dam these car wiper motors not being an easy fit for something they weren't designed to do!

At this rate, I am tempted to bypass the plastic plug connector completely and solder where I need to BUT I don't want to get it wrong and then waste a motor. It's hard when you get parts for free off friends as it's a bit rude to turn around and say"hey this free part you gave me, it's not good enough, I want a better one"

Success! I have now successfully ground isolated my 2 x wiper motors. It took a few attempts and it turns out there there are multiple ground connection points with these motors so it certainly made it interesting. The main and first connection point that i needed to remove was part of the black plastic molded plug connection. I had to hack (gently of course) into this plastic to where the copper tab was soldered to the case. The second point was off one of the brushes which i did first as documented above! But anyway, my motors are now completed safe to use in tandem attached to the same metal frame so I am rather happy to have this ticked off the list.

Before image and highlighting points of interest



Listened to advise and cut a hole in the side of the casing to allow free movement and less chance of chaffing of wire coming from motor brushes.



Main/first connection point from plastic plug to casing



Main/first point removed. Will put a tidy blob of hot glue over this to make sure nothing can touch it.



Inside motor plate showing changes

One problem ticked and signed off means its time for another problem to surface... I'm not sure I am able to fix this one but I am hoping its something silly I have done and not a matter of waiting for another 3 weeks for a replacement board to turn up.

I have wired up all of my boards and electronics ready to do some bench testing with the SMC3 test utility. Instead of waffling trying to explain, here is a bullet list of situation

• PROBLEM - Getting no voltage to either motor output on MM board
• Getting 12.3V to input power side of MM board
• MM power light is illuminated
• Tested both motors by plugging direct into 12V PSU and both are turning at "high speed"
• Uploaded unmodified SMC3 ino code to Arduino
• Using utility software, I can see the manual POT input changes showing on the graph for both motors

Seems odd that i would be getting NO VOLTAGE AT ALL on the output side of the board. If it was a bad chip or something on board, I would expect to see at least a little voltage on one motor connection unless it is completed stuffed. I used the following testing method: