Help on a timing circuit please :)

[dambit]

Hi All,

I am hoping to get some help on a timing circuit I need to build.

I need to have a spark plug fire every 10 or 20 revolutions that a shaft makes. I am guessing I would need a hall effect sensor and maybe a 555 timing chip/circuit of some kind, but not sure how to go about making it. Any help would be greatly appreciated.

Cheers,

Steve

[FRC]

Also Interested

I am also interested in achieving similar timing. One could achieve it mechanically by using two gears, one larger, and one smaller. But a circuit would be better. Hope someone knows how.

FRC

[gyula]

Hi All,

I am hoping to get some help on a timing circuit I need to build.

I need to have a spark plug fire every 10 or 20 revolutions that a shaft makes. I am guessing I would need a hall effect sensor and maybe a 555 timing chip/circuit of some kind, but not sure how to go about making it. Any help would be greatly appreciated.

Cheers,

Steve

Hi Steve,

One possibility is to use the CMOS 4017 decade counter, learn about it here:
4017 Decade Counter and here: The 4017B Decade Counter

Instead of the 555 circuit giving the input clock signals to the 4017, you can connect a Hall sensor output to the input clock pin 14 of the 4017: use a 4.7 or 5.6 kOhm pull-up resistor for the Hall output pin to its positive supply pin as its data sheet recommends.
You may use one of the output pins of the 4017 to drive directly a MOSFET switch but it is better to use a dedicated FET driver instead.

Notice that the counter steps ahead for every positive going input clock pulse only i.e. when an input pulse increases from zero to a positive voltage, (clock input is active for the rising edge of the input pulse) this means the counter's any one output will stay high for twice as long as the input clock duration: you have to consider this for your switch on-time.
You can study this here, click on Play button to see how the outputs go high and again low as the clock signal comes periodically:
4017 Decade Counter

You can use a 9V alkaline battery for the supply voltage of the 4017 during your own tests and of course you do not need any LED for the outputs as shown.

Good luck,
Gyula

[Jetijs]

This circuit worked very well for me:




It uses a Bedini type self oscillator that charges up a cap at very high frequency, this cap is then dumped into the primary of the ignition coil via an SCR as soon as the SCR is triggered by an optical interrupter. Worked vell on 3000 RPM and a spark on every revolution.
Hope this helps.
Thanks,
Jetijs

[SilverToGold]

The decade counter is a good choice but you would need to cascade them if you want to go 20-30 rpm's per firing. The 4017 Decade counter goes to 10, so you need 2 or 3 cascaded to get the the timing.

Here is the logic circuit diagram of what it should look like.



The "clock" is just your logic input from the hall sensor.

The circuit basically turns on ONE logic output depending on the count. You just connect the proper firing circuit to the logic output from the cascade.

The output looks like this.

‪4017 Decade Counter‬‏ - YouTube

For the firing circuit, I would use the second half of the Bedini SSG circuit that fires the cap through an SCR. Your output would basically be the output of the opto-isolator in that circuit.

[StweenyA]

Good info here already, I was also going to suggest a counter, then scrolled down, and saw it had already been suggested

It uses a Bedini type self oscillator that charges up a cap at very high frequency, this cap is then dumped into the primary of the ignition coil via an SCR as soon as the SCR is triggered by an optical interrupter. Worked vell on 3000 RPM and a spark on every revolution.
Hope this helps.
Thanks,
Jetijs

Greetings Jetijs, what exactly is the purpose of your circuit? It looks interesting.

[FRC]

Zhu Zhu

This might be off topic, but would anyone know how to hack a Zhu Zhu pet
hampster to use as a timer. I went looking around for the cat that Lidmotor
and others had and came across a solar bobbing head monkey that would work.
Unfortunately the store that sold them was out of stock. Then I found these Zhu Zhu pets for $3.00 each so bought a few of them. Anyone have any ideas about these ?

http://www.chapters.indigo.ca/toys/Zhu-Zhu-Pets/606324-4294967041-cat.html?s_campaign=goo-Toys%20by%20Brand-E&s_kwcid=TC|5777|zhu%20zhu%20pets||S||6589685942& gclid=CIjE-J7mk6oCFQzHKgodgHikxg


FRC

[dambit]

Thanks for the info all. I have a bit of reading to do now.

The decade counter does sound good, although I would like the ability to adjust the timing ie. I might want to set the timing to fire on every 3rd revolution and then change it to every 12th. Just for example.

Not sure how to do that.

Cheers,

Steve

[freepenguin]

If I build a device that needs precise timing, I'll use a microcontroller that I can play around the timing without hardware dependency.

Arduino looks promising to me. Here is the link (http://arduino.cc/).

[SilverToGold]

Simple, if you understand how it works.... all you have to do is move the "counter" wire to the appropriate pin and move the one right after it to the the reset pin. If you have a cascade with 30 or so outputs, each output represents the count.

Move 2 wires and you can have any number you want up to the limit of your cascaded counters.

If you want to get a little fancy, you could also cascade some rotary switches to do it in a little more user friendly fashion.

If you decide to use a micro controller, you could just have 2 push buttons that move the counter up or down and also display it onto a little display. Nice if you know how to do it but makes replication a little more difficult for others since they may not know how to program a micro controller and each micro controller is different.

Thanks for the info all. I have a bit of reading to do now.

The decade counter does sound good, although I would like the ability to adjust the timing ie. I might want to set the timing to fire on every 3rd revolution and then change it to every 12th. Just for example.

Not sure how to do that.

Cheers,

Steve

[Jetijs]

Thanks for the info all. I have a bit of reading to do now.

The decade counter does sound good, although I would like the ability to adjust the timing ie. I might want to set the timing to fire on every 3rd revolution and then change it to every 12th. Just for example.

Not sure how to do that.

Cheers,

Steve

Sorry, I misunderstood your needs. I thought that you need a spark on every revolution at speeds of 20-30RPM. In this case my circuit will not work for you.
Sorry.