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I would like to tap into analog signal of Garrett AT MAX metal detector (ínfo) and read the value using arduino analog in. Schematics for the metal detector can be found here

It seems to me that the most interesting pins are FAL/FAH and PTAL/PTAH. From what I understand they are the actual amplified/ filtered signal feeded to KL4X.

  1. What are outputs of FAL/FAH and PTAL/PTAH?

  2. Is it safe to connect arduino analog in to the pins (14,16,18,26) of KL4X and read the values (seems to be 0-4v)?

  3. I would also like to know what pins FREQ1, FREQ2 and AZCNT are.

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  • \$\begingroup\$ Reading analogue & AC voltages at the points shown with a 0-5 VDC scale ADCV should be entirely safe. Do you have a link to the full circuit. If there is an operator usable output (headphones / meter / that would seem a useful interface point. Seeing more of the circuit would help. Fxxx & Pxxx appear tp be two identical channels - possibly from coils in mechanical orthogonal orientation. xxxL and xxxH appear to be low and high level outputs, wity additional filtering for the latter. \$\endgroup\$ – Russell McMahon Apr 19 at 11:10
  • \$\begingroup\$ WHEN Aazcnt IS HIGH FET Q11 is enabled, turining on transmission gates U4A and U4D and feeding signal to the two channels. || FREQ??? \$\endgroup\$ – Russell McMahon Apr 19 at 11:13
  • \$\begingroup\$ Here is the link \$\endgroup\$ – Ant Apr 19 at 11:21
  • \$\begingroup\$ The detector shows metal ID which ranges from 0 to 100 (iron 0-40, anything else +40) and is displayed on the screen. I think the ID is calculated by the microprocessor? I'm thinking that maybe I could figure out the method of calculating the metal ID by tapping into those 4 outputs and create different audio/visual output for the data as the current sound made by the metal detector has only one tone for all metals (All metal mode). \$\endgroup\$ – Ant Apr 19 at 11:34

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