Shield TLE5206

[Joshua]

I thought I would provide a link in this thread, just to make sure it is well-publicized.

@Joshua

Hey, I wanted to pull a recommendation from another post into this thread.

There was a recommendation to put a 0.01 uf capacitor on the receiver end of the encoder wires. This reduced the high frequency electrical noise coming from the wires, and reduced/eliminated the occurrence of false positive and negative pulse-detections. Can capacitors be added to the board, to serve this purpose? We need to be careful to appropriately size the capacitors, so they don’t cause missed pulses.

Here is a link to the thread:

• 2nd Generation MaslowCNC Controller on GRBL

Also, this one:

@Joshua

dlang:

you would have to have a false pulse on one wire at the same time as a real
pulse on the other wire (or a second false pulse on the other wire) before your
count would be off.

That is not true.

• You could have two simultaneous false-pulses.
• You could have two false-pulses that happen in coordination:
  • one high followed by the other high
  • one low followed by the other high
  • etc.

I am not so sure that this is such an infrequent thing. The processor operates at a 16 megahertz rate. That means there is the potential for 16X10^6 false positives/negatives every second. The probabilities don’t have to be very high for this to happen on a regular basis. It is not a question of -if- it happens, but how frequently.

Further, the external circumstances that cause false-positives and false-negatives happen very similarly for both encoder lines. In other words, both encoder wires are subject to the same EMF noise that causes voltage deviations. If there is a positive voltage deviation on one line, the other line is subject to the same environment, and likely experiences the same positive voltage deviation. So, if one encoder line experiences a false-positive pulse, it is very likely the other encoder line will, too, because they are run in parallel and receive the same ambient noise.

dlang:

Adding a cap to the wire will reduce false pulses but it will also slow down
real pulses, so I’m not sure how much it will help vs hurt. I would shield the
wires first.

I agree with as a potential issue. However, if we appropriately size the capacitors, this won’t happen.

dlang:

I would shield the wires first.

I like the idea of shielding the wires, and I think it is a very good step. However, capacitors cost something like $.01, which is a really cheap and easy modification. I would like to do both, because I see this as an unknown. I would really like to see some community members do some work to analyze this; both the effect of the capacitor and the shielded wire.