Near Intersection of I-35 & I-90 Southern Mn. | I've messed with Arduino a bit but not for your type projects. Concerning the pins for your Early Riser. I am quite solid on the their purposes. I'm not so positive on the pin numbers. One Pin on the Early Riser plug is to provide a 12V power source for a real radar gun or the hockey puck GPS. Another Pin is Ground. which is ground for the power for the radar or hockey puck and signal ground. Another Pin is the actual signal itself (which is the whole reason for doing this).
I'm thinking that Pin 1 is ground, Pin 2 signal, Pin 3 is 12V iIN and Pin 4 is radar detect (12V OUT when attached to a radar gun).
The fourth pin is sometimes used and sometimes not even present. With certain Early Riser planter modules, the operator had the choice of using a radar gun or a ground speed sensor. Rather than having a switch so the operator could make the choice it was done automatically. Here's how: inside the Dickey John radar gun the pin receiving the 12V power has a loop back to Pin 4. Pin 4 on the monitor side will then receive 12V if it is connected to a radar gun. If it is connected to a ground speed sensor there is no pin 4 so the monitor would NOT see 12V on Pin 4.
This means that upon initial startup, the program inside the Early Riser polls pin 4 to decide whether a radar gun is attached. If so the program uses a routine appropriate for radar speed, otherwise it assumes a ground speed sensor and behaves differently.
I ran into this when I would make adapters to use a radar gun already in the tractor to an Early Riser Monitor. I had to provide 12V on the Pin 4 so that the Early Riser would perform properly.
My opinion is that the signal produced by a real radar gun or a GPS speed device is the common short to ground routine used by flow meters and most ground speed sensors. I am of the opinion that the system "counts" the pulses in a given unit of time and uses the speed Cal number to convert those pulses to usable units of distance and speed. So I believe that the output from the Arduino would only need to vary the speed or frequency to provide a signal for the Early Riser.
I agree on the 57Hz value since some GPS units that can produce emulated radar OUT have a menu choice to set the frequency. By trial & error I have found that setting them at 57Hz produces an output similar to a radar gun thus allowing the device to use its "old" speed cal number. I don't know the mathematical meaning of the 57HZ but it must mean 57HZ is produced at a certain ground speed or distance. When I turn on the emulated radar out with my Ag Leader 6500, the code contains the number 36.11, 5HZ, 500 and 5. I have no idea what these numbers mean but they cause the 6500 to output a radar like signal that I have back fed into the tractor dash.
I have used speed simulators for Raven 440s etc that were a fairly simple circuit consisting of the old 555 timer and some external components involving a "pot" for adjusting the pulse output.
If I were going to do this with an Arduino, I would first setup up a breadboard and a sketch that just produced an output that went to ground (modified Blink Sketch) to see if I could "see" speed on the device in question (planter monitor, Raven 440 etc). Once this was successful then I would approach getting this information from a GPS shield or other source. |
Tell me about GPS Speed Signal waveform...
