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| Potentiometers that do not work with short cables and work with long cables ... |
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| federico:
Hello everyone ! :) time ago I had a similar problem, and you had solved the problem ! :clap: now I'm doing a project a little bigger, and I ran into the same problem .. |O Quick summary: I bought a LEO Bodnar card to create my personal joystick to drive helicopters, board + 5k potentiometers. the value read by 3 of the 5 potentiometers, does not remain stationary, dances quickly between one value and the other, so also during the game, eg: the pedals are seen that vibrate. I noticed one thing, that ironically, the most distant potentiometers from the board, those with longer cables, are those that do not dance and work well, vice versa, those with the shortest cables and closer to the card are the defective ones. So I tried to add a meter of shielded cable, lengthening the cable of the defective potentiometers ... and surprise: now the potentiometers do not dance anymore ... :wtf: Not being an expert, I hypothesize that the signal is "amortized" "stabilized" during the longer cable run. Or ??? how can I solve the thing? |O It is absurd that I have to put the electronics on another side and stretch all the cables to have a fully functional joystick. can you explain to me what happens and how can I solve the problem? :-// Thanks ! |
| Andy Watson:
I would guess that the longer cables are adding capacitance between the signal and ground - thereby reducing the interferance. Is the metalwork on which the pots are mounted also connected to ground? |
| perieanuo:
Put small chokes series with pot wires or verify your power supply he may add noise And please add details like ps used and wiring Regards,pierre Envoyé de mon iPad en utilisant Tapatalk |
| Zero999:
How long are the cables? I suspect the added capacitance could be stabilising the control loop, therefore eliminating the oscillation. Look up frequency compensation and control theory. Try adding some capacitors. Try 100pF first and increase it, until the oscillation stops. |
| federico:
--- Quote from: Andy Watson on December 05, 2018, 05:19:11 pm ---I would guess that the longer cables are adding capacitance between the signal and ground - thereby reducing the interferance. Is the metalwork on which the pots are mounted also connected to ground? --- End quote --- the structure is detached from the ground, resting on rubber supports. The GND of the electronics is not connected to the structure but only to the GND of the card (therefore to the GND of the USB socket) --- Quote from: perieanuo on December 05, 2018, 05:20:01 pm ---Put small chokes series with pot wires or verify your power supply he may add noise And please add details like ps used and wiring Regards,pierre --- End quote --- small chokes ?, Sorry I do not understand what you mean, I know English, but use the translator for many words and I can not understand. It does not have a PS, because it is powered by the USB cable connected to the computer, it is a Plug & play card. (actually in my PC there are problems of "electrical dispersions" that can also be heard from the speakers) and in my pc works worse than everyone, but it also gives problems with other computers that are in good condition, I tried it on 4 different PCs. The cables are a single shielded cable, with poles inside the diameter of 0.50mm --- Quote from: Hero999 on December 05, 2018, 05:34:45 pm ---How long are the cables? I suspect the added capacitance could be stabilising the control loop, therefore eliminating the oscillation. Look up frequency compensation and control theory. Try adding some capacitors. Try 100pF first and increase it, until the oscillation stops. --- End quote --- The cables are about 40 inches long, and they work. Those that do not work, have cables about 2/3 long. The company LeoBodnar replied, telling me the same thing, he told me to add a 1uf / 16volt capacitor. Leobodanr REPLY You can reduce it by putting a capacitor across your potentiometer GND and +5V pins and across INPUT and GND pins. Something like 1uF 16V capacitors should be fine. I found from my electronics store these: 1uf / 350volt, I told him that I needed 16v, but he told me that 350v is better .... I mounted them, (I attach the design of how I connected them) and the situation has worsened, instead of improving .. I asked leoBodnar for explanations and they never answered me again. Did you mean to mount them like that? Thanks at all for your help |
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