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I have a rpi4 and have successfully replicated the project listed here using the eTape sensor (etape tutorial) I am satisfied with the performance using long breadboard and T-cobbler. In order to make my setup more compact I purchased the pi-EZ connect board. When I connect all the jumper cables; the sensor no longer works and I get a 3.3V reading from the sensor which does't make sense. It should be within 1.0-1.8V in order to convert into a sensible volume. The sensor does require 3.3V to run; and I'm just getting that value back? I double checked the jumper cables and even tried different cables; but I can't get it to work. I re-assembled with the t-cobbler and breadboard and it works. Not sure if the pi-ez board is bad? The little circuit chip on the right in the photo is the MCP3008. Would like some suggestions or advice on what troubleshooting steps to take from here. Thanks.

rpi

tlfong01
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Spencer Trinh
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  • Ah, let me see. I read the tutorial you mentioned and found it runs on Windows Visual Studio. So I guess you are running Win VS C# to test the eTape. Please correct me if I misunderstand your set up. Now I guess you are now porting the Win C# program to Rpi Mono C#. If my guess is correct, please give me the program listing and perhaps I can try debugging the section related to MCP3008. Another workaround is to forget Mono C# and borrow some python MCP3008 somewhere. – tlfong01 Feb 05 '20 at 01:50
  • (:)　eTape Liquid Level Sensor on SPI MCP3008 (Rpi2 Win10 IoT Core) - Daniel Porrey, hackster.io 2015sep16 https://www.hackster.io/porrey/etape-f4b457

    (:)　12" eTape Liquid Level Sensor + extras - AdaFruit US$40 https://www.adafruit.com/product/464

    (:)　Porrey Mcp3008 Source Code https://github.com/porrey/IoT/tree/master/source/IoT%20Devices%20and%20Sensors/Porrey.Uwp.IoT.Sensors.Mcp3008

    (:)　YouTube eTape Liquid Level Sensor on MCP3008 (Win Visual Studio) - 2015sep12 https://www.youtube.com/watch?time_continue=10&v=-i99uNDeH2k&feature=emb_logo

     – tlfong01 Feb 05 '20 at 01:50
  • hi tlfong01, thanks for reply. I am not using C#. I am using python with the adafruit library. Here is my github: https://github.com/sktrinh12/tip_novus/tree/master/eTape_sensor . It works fine when using a T-cobbler and the breadboard; but the leds don't turn on and the voltage is not right when I hook up this ez-pi connect board – Spencer Trinh Feb 05 '20 at 02:51
  • Thanks for the clarification. If you are using AdaFruit python library, then there should be no big deal. Most likely it is just a careless wiring mistake, or an intermittently poor contact problem. Perhaps I should check your github python library later. Cheers. PS - I remember I saw your breakout board a couple of times in other forums. It is easy for newbies to misinterpret the tracing and short or open pins. – tlfong01 Feb 05 '20 at 03:21
  • is there a good method to try to troubleshoot? How would i test if there is a short ? – Spencer Trinh Feb 05 '20 at 03:55
  • Ah the standard method for both newbies, ninjas, and hobbyist/industrial/medical/military/NASA grade professionals is the following: (1) Get a multi-meter use the "connected/disconnected" option to test all point to point resistance: near zero resistance would sound a beep, otherwise LCD screen show our of range resistance. (2) Use big resistance option to check resistance value of physical/electrical "neighoubring" points, which should read big resistance, say over one mega ohm. Of course the two test points might have other circuits connected. So smaller resistance might be OK. / to cont, . – tlfong01 Feb 05 '20 at 04:51
  • (3) Might also be useful to test points witch should pull up to Vcc or ground (usually 4k7 to 10k). Now you need a schematic to check that out. Actually there are other tests. For example, for MCP3008, you might need to use SPI "loopback" tests (search this forum for spi loopback programs), .. Ah lunch time. See you later. – tlfong01 Feb 05 '20 at 04:53
  • (4) I forgot to add that to do open/short testing using a mult-meter, you MUST POWER OFF!!!. (5) You might also need to use mult-meter to do voltage check. This time you should use the DC voltage 10V DC or similar range, and see if the voltage level of "some" points are Vcc or Ground level. Power on this time of course. WARNING - No guarantee no nothing won't meltdown or blow up, but then your dirt cheep US$5 multi-meter might also have a fuse to save its life! – tlfong01 Feb 05 '20 at 04:59
  • You python program using linear regression algorithm is a bit newbie scary. For troubleshooting, you may like to try a simple bare bone MCP3008 ADC python program for reference, such as this one: https://raspberrypi.stackexchange.com/questions/99550/how-to-use-rpi-python-to-read-spi-mcp3008-adc-of-a-water-tank-level-sensor. – tlfong01 Feb 05 '20 at 06:33
  • In case you find the above answer "blurred", because of too many down votes, you might try to read this "clear" version: https://penzu.com/p/e800ce64. – tlfong01 Feb 05 '20 at 06:37
  • In case you find the long list of MCP3008 references overwhelming, let me summarize the test in 3 big steps:

    (a) Use SPI loopback to test looping back three bytes,

    (b). Use the same loop back three bytes program to test MCP3008.

    You can find the details in the following question and long CHAT RECORD:

    (1) MCP3008 outputting just 0 Question: https://raspberrypi.stackexchange.com/questions/106728/mcp3008-outputting-just-0

    (2) MCP3008 outputting just 0 Chat Record: https://chat.stackexchange.com/rooms/102745/discussion-between-tlfong01-and-aubrey-champagne.

     – tlfong01 Feb 05 '20 at 08:03
  • More references: (1) PiEzConnect Board - AdaFruit https://cdn-shop.adafruit.com/product-files/2711/EzConnect.pdf

    (2) Pi-EzConnect - Connect and access all GPIO's on Raspberry Pi - YouTube https://www.youtube.com/watch?v=oChXSE0etQw&feature=youtu.be

     – tlfong01 Feb 05 '20 at 08:33
  • wow, thanks for all the info. i have a lot of homework to do! – Spencer Trinh Feb 06 '20 at 03:42
  • you are welcome. Take your time, go slow. Happy python MCP3008 programming! Cheers. – tlfong01 Feb 06 '20 at 04:46

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