The project is back. I found a suitable box (not great but it works). I can't find documentation on the injector timings to have something to work with, I decided to probe the injectors directly in the car.
next step is to make a more refined circuit to remove the protective diode and find a smaller mosfet (I don't really need a TO-220 for the job)
Nothing really fancy, the tester control the coil of the injector with different patterns. There's a few unit on the chinese market but they look pretty crap with their plastic case. This unit will be made for proper abusive workspace with a aluminium case.
Originally I wanted to make a 4 channel unit to be able to do test pattern for all the injector at once. But I realised there weren't resistors but coils that control the injector pin. On my Daewoo car, the impedance is 15.4R which means a lot of current ! (some units are even lower) which complexifies quite a bit the desing if I go this road.
The microcontroller is a STM32F0 that I have in stock in its SOP20 package. I added CMOS buffer to be able to use different kind of N-Channel mosfet to control the coil. Everything will be done with the PWM mode on the microcontroller that has an interesting "repetition" feature which is exactly what I want.
At the moment I still need to find documentation on the duration of the pulses depending on the condition (idle car, fast engine rev, ect...).
as far as I know the injectors on modern cars are digitally controlled by the on board computer. On my car which is from 2000 it's very rudimentary. The CPU controlled the ON time and the frequency of each injector depending on the various sensor readings (throttle position sensor, crankshaft, air pressure, ...). It's really a digital signal for the command control. However the coil has inertia.
the tester will be useful to determine if the injector channel is clogged or has debris in it. The test pattern could be useful to see if the coil is responding at different speed. On this project there will be a mode were the channel is always on to allow cleaner substance to go through.
That's interesting -- what do you need to do to test an injector? Is it a simple pulse train, or does the injector respond to control voltage proportionally?
I ask because the only injection system I ever really worked on was back in the early 80s was the Bosch CIS system in the Volkswagen Rabbit, which had completely mechanical injectors IIRC. Curious as to how more recent injection systems work.
thanks for your interest!
as far as I know the injectors on modern cars are digitally controlled by the on board computer. On my car which is from 2000 it's very rudimentary. The CPU controlled the ON time and the frequency of each injector depending on the various sensor readings (throttle position sensor, crankshaft, air pressure, ...). It's really a digital signal for the command control. However the coil has inertia.
the tester will be useful to determine if the injector channel is clogged or has debris in it. The test pattern could be useful to see if the coil is responding at different speed. On this project there will be a mode were the channel is always on to allow cleaner substance to go through.