The engine monitoring computer

OK I decided to take the plunge and go computerized. I purchased an ATOM stamp microcontroller computer and an LCD screen. I know nothing about this kind of stuff but did some reading and with a lot of help from Russ at www.Badbros.net, it is slowly coming together.

I have the stamp talking to the LCD screen and have a tiny eye LED sensor working to read the RPM's. I am using a router for the RPM to make sure it is working. I now need Transducers and other components to make it work.

Click here to see what Russ has been doing at Bad Brothers Racing

Basic Atom microcontroller

This is Basic Atom microcontroller. It is a small computer that runs a version of the basic programming language. In this picture, it is inserted into a breadboard to make it easy for me to attach more wires and components for testing. The large plug is a serial cable that allows me to plug the unit into my PC for programming. All of the programming is done on the PC, and then transferred and stored in the Stamp's nonvolatile memory. The nonvolatile memory means that even if the power is turned off to the stamp, the program code is kept inside. The code will only be erased if I choose to do so, or overwrite it with new code.

By using the Basic ATOM, critical engine functions can be monitored, and controlled automatically. This provides an ease of use for operating the engine, and also an extra level of safety. If the system detects a problem with the engine, it will shut it down. If the system loses power it will also shut down the engine. By providing multiple levels of safety, the system becomes multiply redundant. If any one thing fails, the engine simply will not run. A nice thing to have when there is a large mass of metal rotating at high velocity quite near the operator.

LCD touchscreen

The LCD display is also a touch screen. The screen talks to the Basic ATOM by using three wires. One wire sends data to the stamp, one wire receives data, and the last wire works as a means to control the data flow between the two. Since the screen is a touch screen, it can be used to control engine functions instead of having a panel full of switches.

Tiny EYE photo sensor

The tiny eye is an electronic eye sensor, useful for numerous things such as counting product speeding by on an assembly line. There is an emitter LED which produces a tuned light source, and a detector which receives the signals when they are reflected. By pointing the light source at a spinning mass which is painted half matte black, and half matte white, it will emit pulses. The Basic ATOM can count the pulses and calculate RPM of the engine or anything else we may need to check such as speed of a go cart. To check the speed of a go cart you would count the revolutions of the axle and use a calculation that takes the circumference of the tire into account, so that you can figure the distance traveled in a certain amount of time. Very handy little devices. To check RPM of the engine, just aim it at the compressor nut and do a little math!

Testing the Tiny EYE

To test the tiny EYE, a disc was attached to the router. Part of the disc was painted white to reflect the light back to the sensor. By adjusting the speed of the router, various speeds could be tested. The Tiny EYE passed with flying colors.

The LCD showing output of the Tiny EYE

The Tiny EYE output was connected to a pin on the Stamp, and the count function was used to get the RPM reading. Since the count function can return the number of on and off pulses for a specific amount of time, the test was run using a one second interval. This would return the number of pulses per second, which then only had to be multiplied by 60 to get RPM. Pretty simple.

Engine control parts arrive

I have purchased some more goodies from e bay. I received some transducers to use along with the ATOM stamp. These transducers will monitor the pressures in the engine like the oil , fuel and combustor pressures.

Transducer

The pressure transducers take a pressure and convert it into an electrical current. The output voltage of the current is proportional to the pressure input. The transducers purchased were 20 bar and 60 bar models.

Thread adapters

Because the transducers have British threads I had to purchase some adapters to make them work here in the USA with standard NPT pipe threads. They convert the 1/4" BSP threads to 1/4" NPT pipe threads.

End drilling the manifold

I will be making a test manifold in which I will be able to introduce air at different pressures so that I will be able to read the voltage from the transducers. I will need this information to program the ATOM stamp to read the pressures. The stamp will take that information and send it to the LCD screen for display. It will also be used to aid in controlling the running of the engine. I will be making the manifold on my mini mill. I started with a blank of metal and made a center point on the outer end of the blank. I used a centering drill to start the hole that will go down the length of the blank.

Hole centered on end of manifold

As you can see there is a center hole and a larger hole. The centering bit was used so that the bit does not walk around and the hole goes where it is suppose to go. Then the larger hole is the finish size or close to it. The hole was drilled right to the opposite end, but was stopped short of the opposite side. I did not drill all the way through, because if I had the opening on the opposite side would have to be tapped for a plug to keep the air from escaping. This method just makes things a bit quicker and cleaner.

Drilling the manifold outlets

The holes on the side of the manifold are drilled the same way using a self centering bit. The holes on go half way through the blank, and will be the mounting points for the transducers.

Threading the manifold

With the holes in the manifold drilled, they were threaded for the transducers. A 1/4" NPT pipe thread was used to cut the threads into the aluminum blank.

The finished manifold

This is the finished manifold. The regulator will adjust the air pressure being fed to the transducers so that accurate voltage information can be gathered during testing.

The transducers

There is one 20 bar, and one 60 bar transducer mounted on the test manifold. I am using both transducers so that I may see the difference in voltages between each type at all pressures.

Wiring the transducers

The transducers I purchased have a DIN type cap in which all electrical connections are made. I had to attach the wires so that I could supply power to the transducers, and receive the voltage outputs.

Wiring harness

The transducers are wired and now are ready to test. I will be looking for a voltage reading from the transducers. The voltage should increase as the pressure is increased.

Pressure regulator

There is a pressure gauge on the regulator that will tell me the pressure to the transducers and now I need to record them at different pressures.

Voltmeter

With the two different types of transducers, I needed to get a voltage reading from each. The table below shows the output voltage from each transducer and varying input pressures.