Hi
spec
Hi
DerStrom8
Thank you very much for your advises and recommendations.
Spec, I would like to make this tester for a few similar models ignition coils, fitted in most models Renault - Nipondenso, Sagem and Beru. Not an universal tester. I've made some calculations and I've decided that the time to coil induction to be from 2.8 to 10.3 ms - low time of timer. Time to spark - 1 ms. high time. After your instructions my circuit looks like that now: For the timer part I think that everything is ok now. But I think that the part with ignition coil isn't proper. I need help with circuit for it.
Hy milkoni,
No problems- reminds me of fun days with sparks and thunder... and dead components.
I had a go at doing a circuit for your ignition coil tester based on your last circuit. The 555 timer circuit is unchanged, apart from the position of the 'Test' switch. I mentioned that the timer circuit might be more complicated than necessary, but after looking at it in detail I find that it is an optimum design, although I have not analyzed the the actual values, apart from R2 which is a good choice. I have also changed C8, the timing capacitor, from an electrolytic to a solid type as this will give more accurate and consistent timing.
Here are the spark frequencies from tick-over to a typical red line for the most common four-stroke engines:
ENGINE SPEED/CYLINDERS_____1CY____2CY___4CY___6CY___8CY
1000 RPM (tick over)_________8PPS____16____32____48____64
6,000 RPM (red line)_________50PPS___100___200___300___800
The MOSFET has been changed to a 20A 500V version and also the diode in series with the MOSFET is now a 500V 8A version. There are many similar MOSFETs and diodes that will do the job; I have just chosen those that seem to be the most common, reasonably priced, and available. Apart from the voltage and current rating of the diode, a low forward voltage at 5A is the important parameter.
C2 is a car capacitor (condenser) normally connected across the points of cars that still have them. The value is not critical and 100nF to 220nF should be fine. Don't be tempted to use an ordinary capacitor. A heavy duty, high temperature low ESR industrial suppression type capacitor- typically polycarbonate- would be suitable, but that may be much more expensive than a standard car type.
It is important that the circuit is built as shown on the schematic ie thick wires where indicated and the supply rail wiring for the timer and coil separate and only joined at one point where the PSU connects. This is to both protect the 555 timer chip and to reduce the likelihood of the blood and thunder in the coil side from upsetting the operation of the timer. The two diodes and two resistors between the timer output and MOSFET gate also assist in this. The 22 Ohm resistor connected to the gate of the MOSFET should be physically connected directly to MOSFET gate as it also functions as a gate stopper to inhibit any parasitic oscillations.
If you would like to change from multi cycle to single half cycle mode, just short out the diode in series with the MOSFET. The MOSFET substrate diode will then dissipate the energy left in the coil on the negative swing.
A 14.7V supply line is shown on the schematic (15V would be OK but no higher); this represents a typical battery voltage under normal driving conditions. You can also drop the rail voltage to 10V to check the coil under simulated cold cranking battery voltage.
It is quite difficult to do the coil side of the design without proving the various assumptions on the bench as you go along. Also, I have never used a MOSFET to switch a car (auto) coil before, only SCRs and BJTs, but I have used MOSFETs for switching other high current/voltage loads. This is a paper design so please treat it as initial and experimental, and best to check the schematic for errors- even gross errors, which are fairly normal with me at this stage of a project... or any other stage for that matter.
Just a word of caution: there are some very nasty voltages lurching around ignition coils when they are operating, not just the HT side either, so please be careful. I speak from experience here, and have some idea of what it must be like to be hit by a TASER gun.
spec
ERRATA
DATA SHEETS
https://www.ti.com/lit/ds/symlink/lm555.pdf
https://www.vishay.com/docs/91237/91237.pdf
**broken link removed**