dial back timing light, what makes it tick...?

[pishta]

trying to envision making a manual advance retard box out of an old dial back timing light. What electronic circuit does it use to delay the spark impulse to fire the xenon tube? All the delay circuits I look up are seconds, not milliseconds.......at 4000 RPM = 0.000138 seconds per degree! I would like to dial it back up to 8 degrees for a boosted application.

 

[Cuda416]

trying to envision making a manual advance retard box out of an old dial back timing light. What electronic circuit does it use to delay the spark impulse to fire the xenon tube? All the delay circuits I look up are seconds, not milliseconds.......at 4000 RPM = 0.000138 seconds per degree! I would like to dial it back up to 8 degrees for a boosted application.

Sounds like a cool project! You might go look at some of the open source ECU projects and see how they do it. I'm guessing at that level it's not anything like an R/C circuit but rather a signal/freq generator which is tuned by a rheostat.

 

[Cuda416]

Something like this perhaps.

50Hz-6KHz TP354 NE555 Module Square Wave Pulse Generator Oscillator Output Signal Source Frequency Adjustable 200mA DC 5-15V: Amazon.com: Industrial & Scientific

Obviously you'd need something with better specs but this stuff is available.

EDIT: thinking about this, unless I got it wrong, there are 24k ignition events at 6000 rpm in a v8, that's only 400 (24000/60) per second which is well within the range of the oscillator listed.

This is well and good, but As I re-read your post, you're a wanting to have a gadget that you can place into your existing setup I think. Still way cool project and I look forward to see what you come up with.

 

[RustyRatRod]

I've found when you hit the fan with the timing light it ticks purdy dang loud.

 

[azaustin]

I was going to say something with an IC555 chip, but it looks like Cuda416 found one.

 

[67Dart273]

Well I ain't a solid state designer, but this was done a very long time ago. WWII vacuum tube RADAR. RADAR, at least pulse RADAR would not work without various timing circuits. Primarily what are / were generally known, in descrete circuits as "multivibrators."

Multivibrator - Wikipedia

Probably what you need, other than shaping circuits to get whatever pulse you need to the point of a proper trigger, is a "one shot." This means what it implies......You turn it on, it resorts to a "state." Every time you trigger it with a proper pulse, it generates a pulse. You can have variables in the circuit to vary the length of the pulse. That pulse, when selected to the delay you want, could then be used to trigger something else.

They did it back then to less than a microsecond WITH VACUUM TUBES you darn sure can to it now with solid state devices.

I repeat. I am not an engineer. I am not paid to be.

But with chips and "pre made" circuits there has to be many you could use. I'm sure a 555 chip, yes.

"555 Timer variable time delay"

Google Search

Google Search

 

[pishta]

great! I knew of the venerable 555 but I never saw a micro or millisecond delay application. The spark event happens at the end of the pulse so I guess I would just have to extend the pulse or duty cycle of the trigger to get me a delayed event? Interesting.....further research....Ill take a look at my cheap HF dial back tach (or for that matter my dial back MSD box)...DUH! I had forgotton I even had that to see what it uses, probably a blob IC (masked to prevent pirating). we'll see as I dont really want to use that for this application.

 

[67Dart273]

Also bear in mind if this is a distributor, not coil on plug, that you will have to compensate for rotor phasing. On a stock typical dist, the mechanical advance is right on the same shaft as the trigger/ points, so that normally does not change. But the vacuum advance DOES This has to be built into the design, and is why, in some applications, you see weird rotor contact shapes

 

[pishta]

LM358 op-amp and an NE555S were the heart of the dial back TA-2200 dial back mainboard. Along with a few diodes, resistors and transistors, a MOSFET and a huge 680V capacitor to fire the xenon strobe. Not too complicated but nothing Im going to re-engineer for a dial back box. I think the 555 will be the start for a new build. I bet an arduino could do this with a few lines of code. Ill keep this thread informed. Seems someone else besides HF sells this light TL2200 TA2200 Timing Light Tester for 12V Gasoline Engines - Easy Engine Timing Adjustment Tool

 

[67Dart273]

NOTE: I'm not saying a 555 specifically is what you need. There are likely better circuits. I am saying that it s a popular timing circuit and you can learn a lot.

You don't need anything as complicated as a microprocessor or arduino. The timing on a 555 or similar is all analog. You'll need stable components AKA the resistor(s) and cap(s) in the time determining circuit so that once set, they are not going to move much.

What would be ideal would be some of the little mini booklets that RadioShack used to sell on different, simple ICs.

Bear in mind that EG some of the "dial up" lamps were a pot (potentiometer) with a calibrated dial for degrees. You'd have to do that by trial and error. But you can calculate the timing and get it in range, then you'd have to mark the dial/ knob using a timing light for some markers

You could even make something to imitate a vacuum advance. You can get vacuum sensors who's output is variable capacitance, or probably resistance. The changing vacuum modulates the timing circuit for the 555

Also bear in mind that something like that done digitally (arduino) STILL NEEDS an analog to digital converter in the case of a vacuum sensor, so it's simply more layers of complication

Some more "stuff"

https://www.jameco.com/Jameco/workshop/TechTip/555-timer-tutorial.html?srsltid=AfmBOoppQIUyzvmAlSrUagID08vvKrAy-xApqD9to04re_hEW7dkSZfP

 

[pishta]

So no dial back can ADD timing so if your dial back has more to go past 0, then use it. My pot had about 15 more degrees past printed 0 and that was with the locating tab in its correct position. Just an FYI, it may not change anything but may wanna check it.

 

[67Dart273]

No electronic device can invent time travel, so there is only delay. However, it is possible that some circuits delay more than an entire event, giving the APPEARANCE that some settings are "ahead." AKA an ignition system would never know if it is firing no1 at zero degrees, or zero + 360 degrees.

 

[pishta]

yes, I was trying to state that fact in saying if the 0 dial position has anything left past it turn wise that further moved the mark, then that is more likely actual zero (no delay) offset, ie true reading. Probably safe to check them prior to basing your timing off of the stick on scale.