External pulse delay

[yatahaze323]

Hi Everyone,

I'm using my MPP rev-D at the beach and I was curious if anyone changed out the Trimpot and put in an external pot similar to the TDI beach hunter?

I searched the forum but I didn't find anything from anyone else trying this. I thought it might be useful to be able to adjust the pulse delay as I move between the water/wet sand/dry sand.

Any opinions on if this is a good/bad/or pointless idea to implement?

Thanks again everyone!

[Qiaozhi]

Hi Everyone,

I'm using my MPP rev-D at the beach and I was curious if anyone changed out the Trimpot and put in an external pot similar to the TDI beach hunter?

I searched the forum but I didn't find anything from anyone else trying this. I thought it might be useful to be able to adjust the pulse delay as I move between the water/wet sand/dry sand.

Any opinions on if this is a good/bad/or pointless idea to implement?

Thanks again everyone!

The MPP Rev-D already has an external pot for the main sample delay. It's called the Reject pot, as per the original Minipulse design.
The main sample delay trimmer on the PCB is there to set the minimum sample delay when the external Reject pot is at minimum.

[yatahaze323]

Hi Qiaozhi

I think I'm misunderstood how the reject pot funtioned, I re-read parts of the build document specifically this part:

2. The original Minipulse's Reject (sample delay) pot was 50k, but now the minimum possible
sample delay is below 10us, the range of adjustment was found to be insufficient for
rejecting some low conductivity targets such as pulltabs. Hence this pot has been increased
in value to 100k for REV-D, to provide a maximum delay of approximately 32us (when the
minimum delay is set at 10us).

If I'm understanding this correctly, I could change the main sample delay trimmer to lets say 10us and then using the external reject pot adjusts the sample delay between 10us - 32us?

Thank you again for your help!

[Qiaozhi]

If I'm understanding this correctly, I could change the main sample delay trimmer to lets say 10us and then using the external reject pot adjusts the sample delay between 10us - 32us?

Thank you again for your help!

That's correct.

[yatahaze323]

Great! Thank you for helping me understand the difference between the two!