Capacitor Outside Foil Sniffer w/ Arduino Version 2.0r | Improved Accuracy

A couple of changes to the circuit that keeps the analog inputs (A0 & A1) at 0 volts until testing takes place, which provides a more consistent result when trying to discern the outside foil of those low value capacitors. In addition to the schematic and BOM, a few tweaks to the sketch were made as well. You can download a copy of the aforementioned at the link below.
Capacitor Outside Foil Sniffer Version 2.0
drive.google.com/drive/folder...
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A simple circuit using Arduino (and a few other parts) to identify the outside foil or shield of a capacitor for those that don't have an oscilloscope or other means.
This is a new/improved design that omits the OLED, Si5351, step up Audio Transformer and puts less stress on the Relay by limiting the switch cycle to 1 second and leverages two LEDs to identify the outside foil or shield of the capacitor.
You can download the schematic, BOM & sketch at:
drive.google.com/drive/folder...
Just look for the folder: Capacitor Outside Foil Sniffer w/ Arduino Version 2.0
If you missed Capacitor Outside Foil Sniffer w/ Arduino Version 1.0: • Capacitor Outside Foil...
Some other similar circuits I've designed and built in the past:
• Capacitor Outside Foil...
Thanks for watching and subscribing to my channel on vintage radio repair and other related circuits.
#restoreoldradios
#Arduino

[@Wil_Bloodworth]

This is fantastic. Thank you Don!

[@RestoreOldRadios]

William, thank you. Best, Don

[@SBWings]

Hi Don. I noticed on the revised schematic that you also eliminated the ground to pin A2. Was this intentional? Thanks for the update! I finally built v2.0 so I will make the latest changes. I did successfully use my v2.0 to mark several caps that are going into an EICO 324 & a Heathkit SG-8 that I'm restoring. This was my first time building something like this. I've built other kits before but they have the PCB already done. Some things were challenging for me, like lining up the 5th pin on the relay, since it landed between two holes. I finally figured out I could drill a small hole in the PCB and "solder-bridge" the pins to the board.

[@RestoreOldRadios]

Steven - correct, I eliminated the ground to A2 and updated the sketch in the folder as well. With the modification on my prototype build, I was able to eliminate false triggering. It’s great to hear you are using the circuit with success. I would appreciate you keeping me updated if you make the modification and your experience afterwards. All the best. Don

[@Newlife-ol6pk]

No commection to your video whatsover but do you know the best way to connect an external antenna to a radio with an internal only antenna? I've seen that some people connect one end to the telescopic antenna and the other to the ground when it comes to FM band 88-108. On medium wave radios, I've seen that in some schemes the antenna is connected via a coil to the ferrite antenna (transformer) and I think this the best method for AM radios, but does it work in the case of an FM radio? Could an external antenna be connected inductively to that 5 turn antenna? Does it make any sense?

[@RestoreOldRadios]

Reference the video below that compares different FM antennas and their performance, it seems height and a vertical polarized antenna is best. I’ve never tried to inductively couple a FM telescopic antenna. Hope this helps. Best, Don kzbin.info/www/bejne/gICogmirh9Nmbqssi=xYqxZch1inPjDJ4g

[@Newlife-ol6pk]

@@RestoreOldRadios Thank You for your answer and the video.I saw it few days ago ...I don't think my message was clear enough .I was not talking about coupling the telescopic antena but those 5 turns wire with a small coil connected to a an external antenna.. Anyhow thank You for taking time to answer and for Your videos!

[@RestoreOldRadios]

I gave your method & procedure a try with a tweak to the coil around the telescopic antenna. A short video below that captures my results. Thanks again for reaching out. Best, Don kzbin.info/www/bejne/nHqte4apqcmFoKssi=lkXRI9lcakyf_aIT

[@DERB_Seymour_Indiana]

👍👍

[@RestoreOldRadios]

Thanks Doug. Best, Don

[@bzuidgeest]

Wouldn't those changes not decrease the signal level for the analogue inputs? I can barely get a read on most .1uf caps with the old version. It works quit consistently for lower value caps. But I use a lot of .1 and for some it reads barely 1 unit 0.0049v on the measurements. For those that actually measure its usually quit consistent, but a lot just show 0v on both readings. Maybe I should need a bigger signal source than the arduino can create.

[@RestoreOldRadios]

Yes, it does decrease the received signal and eliminates the false positives I was seeing. Again, this modification was aimed at v2.0 based on my prototype build. All the best. Don

[@bzuidgeest]

@@RestoreOldRadios I have build your prototype, but it doesn't produce a measurable signal with caps of 0.1uf (modern ones). Is that something that also happens with your prototype? Or is that just my build. So lowering sensitivity seems the wrong way to go (I barely get any false positives and always repeat test)

[@t1d100]

I am not a strong Arduino person, but I am wondering if the relay and its driver might be eliminated by 1) having the code switch the present output signal pins' duties... The output pin becomes the input pin and the input pin becomes the output pin. Or, if that would not work, maybe three pins could be used... one static reference pin, one positive going pin and one negative going pin... I hope I made that somewhat clearer than mud. What I am trying to to ask is if the Arduino has enough functionality for the circuit to be configured without the need for the relay and its driver...

[@RestoreOldRadios]

My Arduino programming skills are average at best, so hopefully others following this thread will address your question. I appreciate you watching and reaching out. Best, Don

[@t1d100]

@@RestoreOldRadios My programming skills are even less than your average... lol, hence my question. I have looked at the circuit, again, and I am rather confident that it would be a straight-forward adaptation... Remove the relay drive circuitry. Set up another pair of 10K/1% resistors on A2/3, as you have them on A0/1. Make sure A2/3 are turned off. Drive R6 with A0/1. Save the results. Then, make sure that A0/1 are turned off. Next, drive R7 with A2/3 and save those results. Compare the two results to find the highest voltage amplitude, to determine the outside foil orientation. I hope someone comes along that can confirm the idea.

[@markdelvecchio9316]

I would love to have one, but I don’t know how to make boards. This isn’t my trade.

[@RestoreOldRadios]

Thanks for watching. If I ever have some built and sell them, I’ll reach back out. Thanks again. Best, Don