It's Over (A New Tack).

I have given up on building a standalone engine monitor. Several reasons, but the biggest, I can buy basically the basis for $200. Once I started looking at part prices, and all, I decided to look at what is out there. I looked at Dynon, GRT and MGL. 

MGL has a remote data acquisition computer (RDAC) for 4 cylinder engines for about $200. The RDAC XG supports both CAN and RS-232 communication. The CAN bus is the most interesting, since that is how most modern cars talk to their instruments. The device can monitor 4 CHTs, 4 EGTs, Oil Pressure, Oil Temperature, Current, Volts, Tachometer, Fuel Flow, Coolant, and two aux inputs. 

MGL doesn't have the best reputation, but I am sure it is quite reliable compared to anything I can put together, and will be considerably cheaper than the prototype. This unit seems to be the quite capable for what I want. I could still use the phone or tablet as a display. The CAN or RS-232 bus could be converted to USB, Bluetooth, or WiFi. 

There you go. Why would I build something when I could buy it for less. 

So what is my plan? 

Modules! Well, node-red or MQTT modules that can be put anywhere, airplane, tractor, scooter, etc. The RaspberryPI as the hub can allow all kinds of configurations, displays, inputs. These modules can be temperature sensors, pressure sensors, GPSs, IMUs, etc. 

Part Prices

I was looking at laying out a prototype board, something better than the proto board I am using now. I really like the MAX6675 for the thermocouples. The protoboard is looking good with 4 of the Arduino modules on there. I've built some braces for the modules, and it should be good for ground testing. 

I can buy the Arduino modules with the cap from the data sheet, 0.1" pins and a screw terminal for about $4.00 all day long. If I want to buy the bare chip, it is $9.00-$11.00! Why? I thought the Arduino modules might be using a clone chip, but when I magnify the chip, it clearly says MAX6675ISA. Is it counterfeit? I would thing MAXIM, or whoever would be catching these at customs if that were true. I just don't get it. 

I need to do some more research. Find out if there is some magic I am missing. I am sure I could request samples, and probably get what I need for very little, but if someone were to want to reproduce my work, well, it could get very expensive. 

I know I said I ordered 3 meter thermocouples, I was wrong. I ordered 2 meter cables, and boy are they long! I could have gotten away with meter and a half cables for the two front (rear) cylinders, and 1 meter for the back cylinders. Anyway, they aren't built well, so I may need to modify them anyway. The crimp joints don't have any strain relief, and that is where things are likely to break. I 3D printed a brace to support the modules.

The code has been modified for talking to all 4 modules. I think I'll only have 4 on this board, due to space. Eventually I'd like to use 4 more of the same module for the EGT temperature measuring. I am also using the Hall Effect Linear Current Sensor Module ACS712 for Arduino for measuring current to the panel. I haven't the software for that yet. 

I am printing a proto mount for the firewall now. I use tinkercad for these parts. The links are here, if you want to use them. Let me know if you do. 

ProtoMount                       ModuleBrace