RF shielding for my printrbot.

RF shielding for my printrbot. Anyone designed a case with a faraday shield for the Printrboard?

I am playing around with a cheap 434MHz receiver to track my power usage. Problem is, when I’m running my printer I get no data - I’m suspecting the board (possibly the stepper drivers) are spewing RF noise into the area. I have moved things about as far apart as I can. I do have a better receiver on order, but probably should work at reducing the problem at source.

If you know much about the SDR hacks as of late, you can use one to track down the source of RF noise. The motors and wires can be a large source of rf noise, however nothing on the board should be anywhere near 434Mhz.

@Alex_Wiebe ​ you can also try test using tinfoil. (Don’t forget to connect the foil to ground)

@Sebastian_Schmidt That’s going to be a first test. Have to wait for the job to finish (actually thought for a millisecond of trying it live, then slapped myself silly for thinking of bringing tinfoil anywhere near the live board…).

You’re right be carefull and don’t make it live :wink: but that problem can be avoided. You only need a contact to ground the rest of the foil can easy be isolated.
Using paper or plastic foil and glue.
Or you can using cardboard to built a easy housing it must not look good. After you finished it you can wrap the foil outside und glue it to the cardboard.

@Stephanie_A Signal reflections and other resonances can easily reach the MHz and GHz ranges. Try adding ferrite cores to the motor’s and heater’s wires, as shielding only the board itself will have barely any effect unless you’re also properly filtering every single lead going into or out of the enclosure.
However, devices with CE/FCC certification should not emit so much RF that it interferes with other devices in the first place…

AFAIK it’s either the board with its MHz-CPU or a (switching) powersupply nearby. Mostly the PS…

@Alex_Wiebe Motors themselves can also be create noise, but I would check the psu.

Motors? How? They are magnetically sealed…

@Rene_Jurack the wires mostly because they are unshielded.
And if you have a motor that connects the rotor via brushes.
The current will cause arcbursts that are a really good rf noise source :wink:

@Sebastian_Schmidt@Rene_Jurack ​ Yep, that is exactly why spark gap radio transmitters were banned, they transmit with a very large chunk of bandwidth, so people could not fit much in one band. I don’t have a sdr, but I will run my printrbot and see what happens on 434mhz, I think my radio transceiver will cover that band just fine.

We are talking of 3D printers?! These are steppers, driven by usually MUCH MUCH less then 40kHz…

@Rene_Jurack One word - harmonics. GHz signals may interfere and create patterns in lower ranges, and kHz signals may resonate and generate higher frequency one.

The wires to the motors would be the largest source of RF. It would be easy to shield them, or you can find shielded wires, cat5 could work, but you need to think about how the pairs would be coupled. The quick test again is the aluminum foil.

At least going to twisted pair (black/green and red/blue), without shielding, should take out a whole bunch already of whatever’s being emitted.

When I assembled the Simple, I managed to squeeze a choke on the X axis stepper. I have a few more kicking around, I’ll stick them on the leads for the other steppers.

@Thomas_Sanladerer ​ fcc doesn’t regulate the quality of your receiver, and EU only regulates the recovery, so it is possible that the receiver is sensitive to noise.

And depending on what is uses as it’s lf band (could be low MHz, often 10mhz). Coupling could be occurring in the lf position. And fcc regulations get pretty loose at low frequencies.

Twisted pairs will most magnetic field noise, that is really what most of your stepper noise will be, ferites will not do as much as twisted pairs, especially if you don’t have a shunt cap

Also a metal box will not kill all of the noise, it may take it down 20-30db at best

Well choking didn’t help (also, it was a quick job and I didn’t wrap the cables around - just passed through. Put a choke on each of the stepper lines. Also, on whim I wrapped the cable loom that goes to the print head (heater, 2 small fans, temperature and extruder stepper) with aluminum foil tape and secured (loosely) a wire to one of the exposed screw hole pads on the Printrboard.

No dice. Will keep brainstorming. I also have a better receiver on order that I hope will help.