Help with Limit Switches please

[rustyolddo]

Firstly, My main Frame/Chassis has absolutely NO electrical connection with anything at all, not even the Mains Earth.

That is fine though it would be better if it were earth ground just for safety sake.

I put my digital Multimeter between the Resistor Heatsink, (which is also connected to the +16Ve Stepper feeds), and the Frame/Chassis and have a Voltage between 5.5 - 6.5 Volts DC occuring, (Chassis is Negative). There is only one possible source for this, which is RFI from somewhere. .

Not neccessarily, voltage depends on the type of drive you have, I presume this is with the power on. You should have current keeping the steppers locked which could be the 6v that you are seeing. Your RFI is going to show up as AC instead of DC and it will likely be riding on the DC component. Take your DVOM on the 200mV scale with the dremel running but power to the controller off and see if you can find AC voltage on your step & direction lines, confirm by switching the dremel on & off.

I'll try a few small capacitors between the Chassis & Heatsink tomorrow just to see if it goes away. I'll also try connecting the Chassis & Heatsink directly and observe. I've still yet to put the .01uf caps across the Limit Switch inputs, so I'll also do that tomorrow.

Be careful what you connect to ground. Capacitors won't hurt anything but connecting the heat sinks to ground could cause blown componets, again without a schematic, I can only speculate.

[rustyolddo]

I have built up a filter box for the Dremel and also placed a Ferrite Toroid on the Power Lead where it enters the Dremel. The Filter Box consists of a Filter Socket, (like the ones in a Computer PSU), connected to another Filter package, (one of those Alloy Tubular thingys about 50mm dia), which is then connected to my Control Relay and a Mains Socket for the Dremel. All of this is packaged up in a Steel Box which is Earthed to the main Frame. This should stop any Radiated Noise in the cabling at least. I've also placed an earthed sheet of steel on the Frame, between the Dremel and the Cabling.
I haven't had a chance to test it yet, but tomorrow is another day.

The probelm shouldn't require this extensive of a treatment. In fact, you probably could have stuck some .01 caps across the A/C lines to kill the noise. The other noise would would be inductively coupled or generated from the motor coupled into the data/control cable. Tend to think that the speed control on the dremel is more of the culpret than the noise from the brushes.

Regarding the Data Ground, this is where I have all my shields attached. I've also placed .01uf Capacitors across every input to earth which should help.

Again, I think this far exceeds what is neccessary. I'm using plain unshield 8 cond. data wire to drive my motors with 42V P/S. Only noise I got was in my limit switch lines and that's because they share the same cable as the motors. Keep us posted.

[Imagineering]

[QUOTE=rustyolddo][COLOR=Navy]The probelm shouldn't require this extensive of a treatment.

[COLOR=Navy]Again, I think this far exceeds what is neccessary.


I should change my UserName from imagineering to Overengineering