Hi All,
Glad you're here.
I'm running a pulse motor and collecting flyback spikes for battery charging.
When I run the motor with si mosfets every thing works with out the problem that I'm writing about.
When I use sic mosfets the spikes on the scope are about 300v higher which I desire. With the sic fets the MEGA resets the battery swapping sketch repeatedly.
So far I've installed shielded cable for the 20 wires going to the MEGA pins from the battery swapper cct. to the MEGA. ( 4, 4 wire cables, each cable with shielding and ground wire)
All grounds combined and joined to the MEGA ground only at the MEGA end of the cables.
The problem remains.
Next I want to learn how to have AL shielding box and to use caps on each wire going in to the box for the MEGA.
In a previous topic that has been closed there were pics and explanations about this and I have a record of it but still a little ignorant and maybe confused.
The Pic shows a method for this matter.
Surface mount caps are recommended and also feed through caps.
The pic seems to show a resistor and a cap on each wire on the inside of the box.
I thought they were talking about having them on the outside at individual points of entry for each wire and the SMD caps soldered to the "Big thick ground" and to each wire.
If some one is familiar with using shielded cable into a shielding box along this line, I would appreciate your wisdom.
Please show some photos of your current set up, the problem might be in the way it's constructed.
I am not familiar with the terms 'si mosfet' and 'sic fet', perhaps this is my ignorance so please clarify what these are. Part numbers would help, as would a schematic. Hand drawn and photographed is fine.
Your big, thick ground track MUST be on the outside of your box to do any good.. Use tinned. woven wire shields for the wires. Use feed-thru caps for each wire. Spread the shield wires out and solder them around the perimeter of the feed-thru cap.
The orange relays are controlled by the Mega but they are for relaying power for opto switching of fets and the fet drivers. They are not part of the swapper cct.
The photos reveal what I suspected they would, a tangled mess of wires. Each of those random wires makes for a nice little aerial that will transmit or receive interference from one part of the circuit to another.
Look at a piece of cable with 2 wires in it, the current flows down one wire and back through the adjacent wire. Interference in one is cancelled out by the other going in the opposite direction. That's what you have to aim for, the flow and return path for any current are adjacent to each other. In addition, power wires and signal wires should be kept separated as much as possible. There is no point screening things until you have a layout that follows these rules.
Hello Donald,
Please post images in the forum, not as pdf documents, which have to be downloaded to view them.
Sorry but I find the image difficult to follow, but from what I can make out it doesn't help much. Some things I don't understand:
Top left it says 'pos in neg out', which suggests to me there is one wire that is both positive and negative. That can't be right.
Similar top right.
If the black, blue and green lines are wires then they still form loops because they are single conductors, the corresponding return conductor is not with them, actually I don't know where the corresponding conductor's are.
I don't know how anything relates to the devices shown in reply #8.
It would help to have everything mounted on a plate to hold everything in place, I suggest a sheet of aluminium drilled for fixings to hold each device on mounting posts. The plate should be connected to circuit ground.
Possibly start by just laying everything out on a table in a neat arrangement and figuring out how everything goes, and work out wiring runs.
Hi PerryB,
Thanks for responding.
The run battery bank positive connects to the charge bank negative in this type of pulse motor.
I don't need help with that as I've been building this type of cct for 15 yrs.
Obviously I need help with "clean wire" installation and I appreciate your advice.
I'll continue with this setup until I've done a satisfactory job of sufficiently lowering
the EMI so the MEGA functions well while using Sic fets.
In this complete setup I need to use 6 power supplies.
I've been using 5 "wall warts" and an adjustable power supply.
I've run it for 3 days at 12 hours a day and with the si mosfets, it runs well at about 1400rpm. I want to use voltage regulators from a 24v accessory battery instead of "wall warts" 2 -18v, 2-12v, 2-9v and 1-7v: VR's.
I made ctt boards for this and may need help. Got to try the brds first.
"If the black, blue and green lines are wires then they still form loops because they are single conductors, the corresponding return conductor is not with them, actually I don't know where the corresponding conductor's are."
I'm using 8, MEGA controlled SPST 60amp relays in the battery swapping cct.
I have all negative leads to the 2 battery banks in 1 row of 4 relays and all the positive leads on the other row of 4 relays.
It would be easy to use 16amp, STDP relays and send a pair through a single relay.
I want the 60amp capacity and couldn't find SPDT 60amp relays.
I'll reconsider how I've arranged the pos and neg pairs.
Please not that the wires to the batteries on a lower level, travel through holes near where each is connected to the relay.
You can see that the Arduino pin wires will now go unobstructed and all in the same direction.
Please help me understand how to deal with the Arduino pin wires.
I have 4 wire (+ ground wire) shielded cables and now I need advice regarding :
How long or far should they reach from the relay brd.
"Your big, thick ground track MUST be on the outside of your box to do any good.. Use tinned. woven wire shields for the wires. Use feed-thru caps for each wire. Spread the shield wires out and solder them around the perimeter of the feed-thru cap."
Do I need to have individual pin wires with tinned woven wire shields on each one?
I could strip back the insolation on the 4 wire shielded cable and put in a tinned woven wire shield on each individual wire and then put a larger woven shield over the stripped back area and solder as is best.
Feed through capacitors are a little daunting to know what I want to use.
these are less than $4 at digikey and $25 at mouser. Might be a great deal.
Can you point me in a good direction regarding specs for feed through cap.
Hi Paul_KD7HB,
I ordered the feed thru caps that have worked for you. 25days shipping time.
I have a metal box that should accommodate 20 of the caps plus pwr supply leads from a 9v switching regulator for the MEGA.
Maybe I should plan on making another end plate for the box out of FR4 circuit board material.(?)
I'll probably have more questions. Thanks for being here.
Donald
Unless your power supply leads also go through feedthru caps, you are wasting your time and money. Power supply leads are also antennas that conduct noise signals as well as power.
