ErC 6864 on brand new IBTS upgrade

Taking Care of the Bullet R1
1

I’ve installed a new IBTS unit in my V1, and it’s giving very weird RPM values. I’m engaged with support on it, but now it’s the weekend, I’m not resolved, and I’m curious if any users here have seen similar behaviour.

  1. RoasTime sometimes indicates an IBTS RPM of 0. Sometimes it does this – starts out at in the range of 3000-10k RPM and then decays down to nothing.
  2. I put my laser tachometer on the fan, and it’s rock solid at 10k - 11k RPM, and its power supply is a steady 5.2V.
  3. I put my oscilloscope on the yellow RPM sense wire, and I see about 450-500 Hz. The signal amplitude is only about 1.2V, which seems low, but I don’t know a lot about hall effect sensors.
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Support thinks maybe my control PCB is doing something weird, but the 445 Hz on the fan sense wire suggests a fan with a bad sensor to me.

Any thoughts?

2

The tacho signal should be 3.3V when connected to the control board. The pull-up resistor (1k) is located on the control board, so if this is not connected you will get strange readouts or none at all.
If everything is connected but you remove the fan does the signal go high to 3.3V?

3

Awesomesauce, thanks Jacob! With the fan disconnected at the IBTS board, I see 4.75V +/- 0.1V at the control board tach pin.

If I disconnect the IBTS’s 6-position (3-wire) connector from the control PCB, the tach pin on the control PCB appears to be floating.

I have a complete V1->V2 upgrade package incoming. Should I be concerned that this (brand new) IBTS module appears to be pushing 4.75V to a 3.3V logic pin? I’ll just dispose of it if there’s a risk that it will cook my new board.

4

I might not have told you the whole truth.
Depending on the revision of the small PCB holding the IR sensor and connecting the fan, the pull-up resistor could be mounted on that PCB (R1). It pulls the Tacho to 5V.
So to test the fan you would have to disconnect the tacho on the control board side, then it should switch between ~0 and 5V.

5

That helped! I’m getting a solid 5V square wave out of the disconnected fan tach wire. I must indeed have a bad V1 control board here.

The 400Hz signal still seems weird to me but not likely damaging. So unless you think it’s a bad idea, I’m inclined to test this IBTS unit on my new V2 control board once it’s installed.

Many thanks for this help, Jacob!

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