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Need help with zapper module on R2-D2...

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Chris Rice
(@chris-rice)
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I've built a lifesize R2-D2, and installed a working zapper, sorta like the one you see in the movie... I have the whole thing working somewhat, and by that I mean, as long as I keep the zapper prongs close together, it doesn't freak out the other servos, but as soon as I spread them apart more than a millimeter or so, it freaks out the other servos in the system, and could be causing other EMI that I can't see.  I was curious if something like a diode, capacitor, or ferrite bead could be used to eliminate what I'm thinking is some sort of EMI.  Isolating the high voltage (400k V) generator what I call the zapper module, the relay, and power supply, is the only thing giving me any limited success. May have to click on diagram to make picture bigger to read text. Thanks!

skematic

Link to my zapper video

This topic was modified 2 weeks ago 2 times by Chris Rice

   
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Ron
 Ron
(@zander)
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Joined: 4 years ago
Posts: 7140
 

@chris-rice Have you asked the people who created the kit you are assembling what they think? Often these kits get corrected/upgraded but there is no mechanism to disseminate the new information, you need to ask.

Good luck.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@bbutcher85)
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Hello Chris,

This sound like a fun project. Electrical noise can be either conducted or transmitted through the air. The transmitted noise can be either electrical or magnetic in origin. Steel will shield from magnetic noise, and any metal will shield from electrical noise.

There are several things you can try. I am a bit unclear from your diagram about the power connections and where the power to operate the Arduino is obtained. You probably want to have three separate "grounds" in the robot, lets call them Arduino ground, case ground, and zapper ground. For the best results, if these are connected together, do it at a single point. You may get better results with them not connected, or perhaps at a single point. 

Make sure your Arduino power and ground are from a totally separate battery and that there are no connections between either ground or the Arduino battery and the battery used to operate the zapper. 

Place the Arduino and its battery in a steel enclosure that is electrically connected to the frame of the robot (case ground).

Place the relay board, zapper module, and its battery in a separate steel enclosure with a rubber grommet for the low voltage wires and a separate grommet for the high voltage wires. This case will probably also be attached to "Case ground" and the internal electronics ground (zapper ground) will probably not be connected to the box.

Place the two enclosures as far apart as practical. Use a shielded twisted pair of wires for the signal connection between the Arduino and the relay board. One wire will be signal, the other will connect Arduino ground to Zapper ground. Ferrite beads placed on the twisted pair wires (both signal and ground) might help, perhaps at both ends. Place small resistors (R1-R4) between the wires and the connections. If the relay requires more power use smaller resistors than 100 ohms shown. Place ceramic or metallized mylar capacitors (C1, C2) between the wires at both ends to filter out any noise. Choose a low ESR capacitor for this application, and do not use electrolytic capacitors. You want to filter out the high frequency noise.

You may find that it works just fine with only some of the suggested changes, and perhaps the steel enclosures will not be required, or maybe only on the Arduino.

Please let us all know what you did when you get it working.

Bob Butcher

MSEE, retired

Zapper Circuit

 


   
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Chris Rice
(@chris-rice)
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@zander unfortunately this wasn't a kit, and totally custom build. Now other builders have attempted this same project,  but with similar results. I've got it mostly working, by just sheer isolation of components, but just wanted to get to the root cause of what is happening. My skill level with stuff like diodes, ferrite beads, capacitors I would say is at the beginner level, so thats where I kinda get lost a bit. I have been watching a bunch of videos explaining these things, but wanted to start within these forums for help. Thank you for your response!

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Ron
 Ron
(@zander)
Father of a miniature Wookie
Joined: 4 years ago
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@chris-rice In that case very impressive. Check the answer of one of our Electrical Engineer members then for some ideas.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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Chris Rice
(@chris-rice)
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@bbutcher85 thank you so much... We are very much on the same page when it comes to isolating stuff... Gave me some great ideas on a few things to try. I'll get back to you with the results. Thank you very much!


   
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(@davee)
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Hi @chris-rice,

  Circuits with arcs can result in all sorts of issues, and @bbutcher85 has already given some good ideas. Unfortunately Bob was right when he said "Electrical noise can be either conducted or transmitted through the air. ... and so on.", so it usually requires some experiments to figure out which routes are important in each particular case.

My first thought, which might be down a rabbit hole if the conduction is through the air, would be to try using an opto-coupler between the Arduino and the relay, so there are no electrical connections from the arc source, back to the Arduino. The 'traditional' opto-couplers can only pass a few milliAmps in the output circuit, so you would probably need an extra transistor, diode and resistors to act as a relay driver. There are lots of suggestions on the web ... first one Google found for me was at:

https://www.homemade-circuits.com/how-to-drive-relay-through-opto-coupler/

image

This may or may not be a good example, as I haven't read it all carefully, but hopefully gives a clue as to where to start. Have a read about opto-couplers, if they are new to you.

Best wishes, Dave


   
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Chris Rice
(@chris-rice)
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@davee Thank you so much for suggestion... I'm still implementing the first idea, and will see what happens.  I'll keep everyone updated on the results.  This community has been great so far. I do appreciate the help and ideas. Waiting on a couple things I ordered to arrive. Then I can get started...


   
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Chris Rice
(@chris-rice)
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@bbutcher85  it took awhile to get the ceramic capacitors in, and once I got everything connected this solution didn't work for me. I think the resistors dropped the voltages too much for the relay to operate. I'm going to try the opti coupler option next as I think that solution should work. Because it doesn't make a physical connection back to the board, and I think that is where my interference is coming from. I also added more shielding, and that didn't seem to help.  I will keep everyone updated on results.


   
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