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Serial Port Voltage of Ag Devices
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tedbear
Posted 2/22/2021 16:08 (#8851321 - in reply to #8850875)
Subject: RE: Serial Port Voltage of Ag Devices


Don't call it a 'gator, it's a Ranger
I understand your question but don't know the answer. I don't know the voltage level put out by a 252. It may be 12V. It may be 5V. I really doubt that it is 3.3V.

The acceptable input/output voltages with an Arduino depends on the model. A Uno or Nano will put out 5 V but may work with only 3.3V for an input HIGH. I do remember a combination of a WiFi module that worked on 3.3V. I still have this in a drawer. If the logic level on the Arduino was 5V, then they recommended a logic level converter on the Tx line from the Arduino to the Rx of the module. They show an alternative of making a voltage divider with a 1 K ohm and 2 K ohm resistors and connecting the Tx from the Arduino through this to ground. Then connect a wire at the junction in the center of the voltage divider to the Rx of the module. This meant that the WiFi module would only receive 2/3 of the 5V signal which is 3.3V

Going the other way from the Tx of the WiFi module (3.3V) to the Rx of the Arduino Uno (5V) was not a problem. There was no mention of anything dealing with 12V.

I ran into this voltage level concern in a different sort of way. I built a Remote Boom Checker that I plan on using with my sprayer. I used an ESP-32 Dev board which can work with Bluetooth, BLE, WIFI etc. My sketch allows me to use my iPhone, iPad or Android tablet to communicate with the ESP board via BLE. The ESP board runs on 3.3V so having it send out a logic HIGH only produced 3.3V. I needed this HIGH to inform an unused input on my Ag Leader Auxiliary Input Module that I wanted a boom to turn ON. I knew that normally 12V was used as the trigger signal back to the AIM so I assumed I would need a relay or transistor where the 3.3V HIGH from my micro would cycle a relay or trigger a transistor to provide something around 12V back to the AIM. The current demands of the 5 relay board forced me to use a Darlington Array to drive it as the micro couldn't handle the load of triggering 5 relays at once.

One day, I decided to try to see if the HIGH out of one of the GIOP pins on the ESP board was sufficient to trigger the AIM input directly. In other words would 3.3V trigger the input on the AIM or did it need to be something closer to 12V. I was happy to see that it did which eliminated the need for the relays, a Darlington Array and lots of connections.

It appears that "sending less" is sometimes acceptable and things work out. "Sending more" is usually dangerous and may let the smoke out, so I understand your concern but do not know the answer.

I have not tried any GPS experiments. I do have a shield that will allow me to use the GPS from a smartphone into an Arduino but I can understand your desire to use another port of a GPS system you already have. Keep in touch.
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