Electric magnet solenoid with arduino

I built a robot which i want to connect to a trailer. My idea was to use electric magnet soilenoids (40 kg lifting power) for that.

Will those magnets cause EMI and cause problems for the arduino or other sensors on my robot?

Is there another easy way to connect a trailer to a robot without human interference?

Those magnets can even be covered with copperplate so when the connection is made i can power the trailer from the robot (one magnet for dc-plus and one for ground).

To me it sounds like a good plan but what do you think about it?

DC power can never cause EMI. You have to manage some "kicks" when it turns on and off.

Whether they cause interference will depend on the shape/size of the magnets, the way they’re powered, the location of the Arduino with respect to their magnetic fields, and the actual shape of the stray magnetic field from these magnets. It’s indeed only the switching on/off part where you may have problems, after that the field and currents should be stable.

Without having any idea on what this trailer really looks like, no idea on other ways of connecting it easily.

Well i use a 16 relayboard to switch the magnets on/off and that is about 10cm (4 inch) away from the arduino.

The magnets will be about 20 cm (8 inch) away from both and outside the casing (which is plastic).

The trailer is a sweepingmachine (floorsweeping of the carport) and 60x40 cm (25"x20") , about 10-15 kg (20-30lbs) weight.

So which shape of lifting magnets will cause the less EMI? They are round shaped…

If i switch the magnets with solid state relays will there still be EMI ? Or is there another way to avoid any EMI by making a metal shield around the relays or arduino?

I added a picture of both…i want to put that sweeping trailer on casterwheels and connect it straight to the robot so i can also sweep in the corners in small spaces. (i have another spinning brush to mount on the frontside of the sweeper).

When i connect them like a truck it’s not easy to steer the combination in small area’s. The robot steers in tankmode on the big wheels.

It’s all still under development but you’ll get the idea of my plans i guess. I assume that 40kg lifting magnets can do the job if i mount them at the sides of the robot on the frame but feel free to give me your opinion. I have never tested/seen those magnets but they’re cheap and easy to buy online.

In the robotcasing is also a Roboteq controller with processor, about 20cm away from the magnets…those grey things with coolingribs are power transformers which will be very close to the magnets.

Hi,
Ops pic.

Tom.. :slight_smile:

Hi,
How much power will the 40kg lift magnets consume, will they need to be ON all the time.

Tom.... :slight_smile:

TomGeorge:
Hi,
How much power will the 40kg lift magnets consume, will they need to be ON all the time.

Tom.... :slight_smile:

The 40kg model i'm looking at now on ebay consumes 300W at 12Volt dc....and has very thin wires hahaha. Products from china are mostly a waste of time.

https://www.ebay.com/itm/P40-DC-12V-40kg-Electric-Lifting-Magnet-Electromagnet-Solenoid-Lift-Holding/263084749161?rt=nc&_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D49476%26meid%3D24e4ac1a172841f3bd6a7fa18d606260%26pid%3D100005%26rk%3D6%26rkt%3D6%26sd%3D172144511205&_trksid=p2047675.c100005.m2219

But this one looks better, 2A at 12vdc and can pull 55 lbs.
https://www.ebay.com/itm/55-LB-Electric-Lift-Magnet-Electromagnet-Solenoid-Holding-57mm-Robotics-12v-24v/322860335074?hash=item4b2bf9bfe2:g:p6YAAOSw6HJZwtup

The green pack under the robot is the battery, 15Ahr at 36V....2 A at 12vdc is no problem and i will only use it for 30 minutes a time or so.

Maybe i should use open solenoids instead of magnets, is cheaper and doesn't use any power..but then i still need a solution to power the trailer from the robot.

Hi,
Why not put a loop on the trailer and have an arm move down to hook the loop.

Use magnets to couple power, but you would not need electro magnets, just neodymium type in position with springs to connect and pull apart when uncouple and move away.

Placing the magnet pairs above each other and above the end of the arm means very little relative movement.

Just a thought.
Tom… :slight_smile:

Make sure that you have freewheeling diodes in the switching circuit.

TomGeorge:
Hi,
Why not put a loop on the trailer and have an arm move down to hook the loop.

Use magnets to couple power, but you would not need electro magnets, just neodymium type in position with springs to connect and pull apart when uncouple and move away.

Placing the magnet pairs above each other and above the end of the arm means very little relative movement.

Just a thought.
Tom... :slight_smile:

This robot uses tanksteering and with a loop i will have to pull the sweeper. But that's not easy because the trailer will shear when going reverse. It is possible though and i might go for it.

Connecting the trailer and pushing it on casterwheels will be easyier to drive i guess, haven't tested it yet on casters.

I don't understand how i can disconnect the neodymium magnest...that will need a lot of power from a servo arm with a lever.

I will think about it, using electromagnets is not the best solution i think now.

aarg:
Make sure that you have freewheeling diodes in the switching circuit.

And if i use solid state relays? Do i still need the diodes for those?

Not for the solid state relay (there's no inductor in there), but you still need them for the coils of the magnets/solenoids.

I use a 16 relay board like this, does it need an extra diode or is it already onboard next to the led for each relay?

And when i use the 12v actuator to lift the mower does that need an extra diode at the powerlines? That’s complicated cause i use 2 relays for it to go up and down. Still looking for a motorcontroller which can make it go up and down by pwm.

E_rik:
I use a 16 relay board like this, does it need an extra diode or is it already onboard next to the led for each relay?

Check the documentation of the board.
Probably: yes. I don't see them in the image, but that doesn't mean they're not there. Lots of other components there as well.

And when i use the 12v actuator to lift the mower does that need an extra diode at the powerlines? That's complicated cause i use 2 relays for it to go up and down. Still looking for a motorcontroller which can make it go up and down by pwm.

Depends on the actuator.
It's probably easier to just build your own controller. As it's up/down motion I guess you'll need an H-bridge, so four MOSFETs, and they in turn can be controlled by a PWM signal. Ready made motor controllers may work as well of course - just make sure they can handle the current your actuator needs. The latter of course also accounts for such an H-bridge.