Circuit for counting ignition pulses with inductive pickup using LM2907
- Thread starter Ahoo
- Start date
Thank you so much eetechoo.
Can you please explain the LM317L circuit. what is its function????? Why is it there??
Here's another idea, follow this link, there you will find a tachometer circuit based on the 555 that delivers an output current of 0 to 1 mA depending on the engine's RPM. Also, I suggest you browse through the aforementioned site, it's very interesting stuff for beginners.
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A vehicle's 12v electrical system fluctuates between 11- 14v. The LM317L is a voltage regulator configured to produce a constant 9 vdc output. It may actually need to be set lower to about 8vdc.
eT
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Hey eetechoo
I just did some research and found that there are various types of A1203 hall sensors,,,, Now which one do you prefer to use. Secondly did have you checked this circuit yourself practically???
Hi Georacer
Basically I am interested in making a device that can be used to measure the rpm of engine with the help of arduino.
Well, there's basically two ways around it... either you convert the engine's ignition frequency to a voltage, and then make arduino do an analog-to-digital conversion, or you sense the ignition's pulses and then count the elapsed time between them (using the aforementioned hall-effect sensor). The former option requires more complex circuitry and calibration, while the latter requires very simple circuitry and slightly more complex programming in the arduino.
Personally, I'd go for the elapsed time measurement option, since it's electronically much simpler, and my real strength lies in device programming; although I specialize in the 8051 architecture and have never used arduino before.
Hi Cmartinez
Can you please shed some light on the second method (counting pulses and measuring elapsed time) please.... I know its easy but am not good in programming,, and that was the basic reason for me to go for translating my frequency into linear voltage with LM2907 or 2917, because programming then become quite easy.
and are you guys sure that the hall sensor A1203 as mentioned by "eetech00" will be capable of detecting the magnetic field created by ignition pulses... like what order magnitude approximately that magnetic field strength will be in Gauss when current pass through the ignition cable of engine??????????
Dear Administrator
this topic is not basically related in any way to AUTOMOTIVE MODIFICATION as in ToS,,,, In fact its a general topic and can be used any where besides automotive applications... In fact this topic is more related to counting frequency with micro controller.
I agree, this a monitoring project, and not a modification one, so no part of an automotive system will be affected in any way.
Now, following your request, in order to count the time elapsed between pulses of any signal (and not one necessarily related to automotive) you would have to do your programming using assembly language. That way you would know the exact number of cycles that each instruction in your program would take.
Let's say you wait for your input signal to change its state from high to low, from that point you would call a routine that would start counting a register up until the same signal goes back to low, and then back to high again, that way you would be measuring the elapsed time between the raising edges of the signal, since you would also know the oscillator frequency that your MCU is running at. But as I said, for this to work properly, you'd have to do all your programming in assembly language, so that you will know the exact number of MCU cycles taken between rising edges. This is because each instruction in assembly takes a known amount of clock cycles to be executed, and that is something that you can easily (but also meticulously) track. If you use C, or BASIC or any other language, the compiler will translate your program into assembly anyway, but you won't be able to know the exact number of cycles between the signal's rising edges, since you won't know the exact machine instructions that your compiler generated when it processed your program.
That's why I prefer the 8051 architecture, it's simpler and easier than most other MCU's, and it's far more powerful than most people give it credit for.
MaxHeadRoom
- Joined Jul 18, 2013
- 28,681
For just measuring the rpm I still think the H.V. ignition is a last resort method, especially converting a pulse to a analogue signal which is not so precise?
It does not sound that you need the ignition timing, just total rpm?
If so there are a usually few places you could detect a rotating part of the engine with the sealed Honeywelll type sensor in post #10 or other industrial strength types.
If it has the older point system, there is also a place there that could be monitored, although the prox method is less invasive.
The CCP Capture module in Picmicro's specifically target this type of application
Max.
Hi
There's only two types of the A1203: SOT or SIP, and since I have no idea how you intend to mount/connect the sensor, I can't answer that question.
The circuit works as shown on the schematic simulation (post #22), and it also works on the bench. You'll have to do the rest of the testing and decide what to do next for yourself.
In going forward, keep in mind this is a HW approach to a solution. Other posters have made suggestions doing this in the Arduino, and I agree. It would be a better use of the existing resources you have to use the Arduino. I would have used a PIC micro to do this, but that's just me.
good luck...
eT
thank you eetech00Hi
There's only two types of the A1203: SOT or SIP, and since I have no idea how you intend to mount/connect the sensor, I can't answer that question.
The circuit works as shown on the schematic simulation (post #22), and it also works on the bench. You'll have to do the rest of the testing and decide what to do next for yourself.
In going forward, keep in mind this is a HW approach to a solution. Other posters have made suggestions doing this in the Arduino, and I agree. It would be a better use of the existing resources you have to use the Arduino. I would have used a PIC micro to do this, but that's just me.
good luck...
eT
what do you think what order magnitude the magnetic field strength will be around the ignition cables...
& can you please help me programming arduino for counting these pulses coming from hall sensor like if I want to exclude LM2917 form the cricuit, If you don't mind.
Dr.killjoy
- Joined Apr 28, 2013
- 1,196
What about using about using a timing light ??? Also whats the application for ??? Cause modern cars have the coils attach directly to the spark plug and its a lot easier to buy a blue tooth ODB scanner for $10 bucks and watch it on the scan tool ...
Dr.killjoy
- Joined Apr 28, 2013
- 1,196
Also they make cheap rpm meter with mag pickup too on eBay... I almost forgot that some cars have a waste spark system and this will screw up you end results and sometimes spark systems have a multi spark ignition..
Hi
I haven't actually measured the field around a spark plug wire, but its strong enough to be sensed by a wire wrap or inductive pickup, so it can easily be sensed by a hall sensor.
In addition, the circuitry used for spark sensing must include signal conditioning before input to the remaining circuitry (ADC or otherwise). The A1203 is a hall bipolar switch that already contains conditioning circuitry. It can provides a pulsed DC output (triggered by the sensed spark) at whatever output voltage level needed (up to 30vdc). Cost is about 1.80 USD for the SIP version.
You could send the output of the hall sensor directly to the input of the Arduino (with appropriate overvoltage protection), compute the measured RPM, then display on an LCD, LM3914 with LEDs, or other display device. I haven't used Arduino before, only PIC micro's. Maybe someone else in this forum can help.
eT
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