not much progress this week

this weekend busy with some wedding receptions. The sensorless rpm meter progress was slow. Still struggling to get the right amount of lag filter into the codes.

The display is also a bit too dim for HUD during the midday. Will try to perfect this thing next week.

Update of sensorless engine rpm meter

This is the project built onto strip board. It was quite a challenging project. The idea is to display this as a HUD (head up display) on the windscreen of my old kancil. That is what the 7segment LEDs for. I am hoping that the LEDs are bright enough to be projected onto the windscreen.

Haven't soldered the components yet. It took me a few hours just to put the component together.

Can't wait to solder everything and test it. Now I have to run my other errands first .....

Engine Oxygen Sensor reader

This is just for fun. Another weekend project for the weekend warriors.

For most modern engines, there is air fuel ratio control to ensure efficient operation. Mostly aimed at reducing those harmful gases of the exhaust that destroys the environment. Also, it helps protect the catalyst. Too rich mixture can melt the catalyst.

Items

1. PIC16F676 - (RM8)

2. 7805 power regulator - (RM1)

3. Capacitor (ceramic) -(RM0.3 x 4=RM1.20)

4. Capacitors (e caps) -(RM2)

5. Resistors -(RM0.05x3=RM0.15)

6. KK connector7 way (male and female) and 4 way– (RM5?)

7. IC socket for the PIC16f676 -(RM1)

8. 4MHz crystal - RM(2.50)

9. strip board/vero board -RM(6.50)

10. diode 1N4007 -(RM0.30)

Tools

1. Solder

2. Pic programmer

3. Any compiler for PIC (I use PICBASICPro)

4. Download free Selmaware StampPlotLite

5. USB to Serial (COMport) converter – you can get it from computer stores.

Depending on the engine make, the voltage signal from the oxygen sensor vary. On my TOYOTA it is about 0.1 to 0.8 volts. I think for PROTON also about the same. Actually, what I built was just voltage meter, and plotted the voltage read out on the laptop.

First build the thing. The source codes is here. The source codes is in PICBASICPro. The hex file is here.

The schematics is here.

To connect the 9pin com port to the board – ground to pin5 of the 9pin port, serial out to pin 2 of the 9pin port.

Get the free Selmaware StampPlotLite. http://www.selmaware.com/stampplot/

Find the wires that leads to the oxygen sensor of the engine. Depending on the sensor type, comes with either 2 or 4 wires. Usually for the 4 wires, the black is ground,the red is 12v and one of the lighter coloured is the signal. First using multimeter. With engine ON, find the one that appears to have fluctuating signal.

Here is an example of the signal from the oxygen sensor. I save the data to excel. Note that there is a lot of noise in the data. I suspect that the noise comes from the poor serial communication ( there is a lot of invalid data coming in). I think that it is due to the inaccuracy of the crystal. Need to change that.

Still Alive...!

Man...! It has been 2 years since the last time I tried to write something.

Actually I did complete part of the robot. However, my computer went out of order and I lost all the source codes, pictures and everything. The BASIC STAMP was also damaged, for reasons I couldnot understand. And I had already dismantled the project.

This blog is actually meant as a medium for me to document all my doings. Hence I will try to put something on the robot project as well as other projects. There were also several other projects that I completed during this past years. The robot car, the stroboscope using LEDs, engine rpm counter/display (on laptop), engine lambda reader and water pump (hand operated) using PVC pipes.

First on the robot toy car project.

As I can remember it the following are the items used.
1. BASIC STAMP as the main controller (I don't know the price, maybe a few hundreds ringgits. There is cheaper option, using PIC microcontroller. PIC16F676 would be appropriate for RM9 only - 1k program memory, ADC, 12 IO ports)
2.L293D for motor driver (RM13)
3. light sensitive resistor. I don't know the porper name of this thing.... oh ya photoresistor?
4. resistors (RM0.05each)
5. capacitors(RM0.30 each)
6. breadboard for constructing thecircuit (RM15)
7. The RC car. battery operated. (RM50?)

One of the trouble with the operation was that the motor (DC motor) was quite powerful and draw a lot of current. The battery pack need to be adequate. I remember using 2 separate source of power for the STAMP and the motor. Otherwise the motor would draw so much current that the STAMP stopped working.

The other issue was the turning radius of the car. This made it to lost track of the light easily. In most wheeled robots, the robotcan turn on its axis and face the light. The way I overcame this is by having the car to make very fast three point turns everytime it sense that the light was lighter on one side. It is fun to see it making small three point turns in very rapid movement. Effectively one can see the robot to shake and turn towards the light source.

Unfortunately all the source codes were missing. I will see whether I can salvage the source codes from my old hard disk and post it here.

Next post will describe the toy car, its drive motor and the steering system.

Robot building: 1st post

Okay, this is my real 1st post.

I’ve promised my son that I’ll show him how to make an autonomous robot by the time he reach 9. That was 2 years ago. Now he is almost 10. That promise was never fulfilled.

Guilty conscious, I have scrambled for the past several months to find ways to get it done. Luckily, I saw one advertisement for a workshop on robot building for 9-12 year olds during one of the school holidays. I sent my son, and his cousin, for that one day workshop. It cost me RM125. There, they were taught how to build robots by using the LEGO Mindstorm set. Interested, I asked the instructor how much it would cost to buy one of those sets.. RM3000! I later asked Sasbadi (the agent for LEGO Mindstorm in Malaysia) and found that the minimum set would cost me around RM2000!

I feel that it was too expensive. And I was convinced that to make the robot from scratch would be more fun.

Electronics is not my area, let alone robotics. However, I was determined to learn and build one on my own. I own one Parallax Basic Stamp2 microcontroller, which I bought six years ago. One good thing about Parallax is that they have good website with a lot of information. They also have robotics teaching modules for their Board of Education single board computer (?). That would be useful.

Here is the plan for the robot that I would like to make. I used a cheap radio control car as the base with all the drive motor, steering motor, wheels, and the chassis. This cheap RC car employs DC motors only. There is no servo motor. I will have to figure out how to drive this motors.

Since it is based on a RC car, I need to figure out how the robot would have to maneuvre e.g. through obstacles etc. with a slightly different technique as opposed to using 2 servo motors.

I plan to have photo sensors to make the robot either folllow or run away from bright light.

I will put the detail of the parts list in the next post.