advice on building a momentary circuit

[crazymofo]

Gday folks,

1st post here, hope to learn lots about electronics, its something that has always interested me, but im forever confused about what does what! my level of electronics only goes as far as building kits to make rev limiters and shift lights and such, but these come with all the bits and instructions for dummies. Ive never created a circuit from scratch, and honestly find the process of it slightly un-nerving.

so with that...

Im looking to build a circuit that will cut power or gound the ignition coils of my motorcycle for a set period of time (approx. 65 milliseconds) when I press a momentary switch, irrespective of how long I press the switch for, the "kill" time needs to be the pre-set value.

I think I will need a micro processor (555?) and maybe a switching relay? maybe a trim pot to alter the time the kill stands for as well? but beyond that im not entirely sure where to even start! The bikes side stand safety switch acts as an ignition cut but the way it runs is when the switch is activated it allows the bike to run, but once the switch goes open it kills the bike. so i plan on tapping into that if possible, as this circut from what i can tell does not see any major voltage from the coils. I'll attach a wiring diagram of the bike and hope it helps.

so basically im wanting to create a circuit board that I can run to the current power supply to my ignition coils. once I depress a switch, the board will activate a "kill" in the power for 65 milliseconds, thus the engine stops producing power for that time, allowing me to shift gears quicker. in effect im wating to build a "quickshifter". once the allotted time has passed, power would resume to the coils, even if I am still holding the switch down, the system would reset once I have let go of the switch, ready to do it again for the next switch.

Im not fixed into any type of thought to get this done, so if any help that gets me closer to the goal would be greatly appreciated.

cheers.joe.

 

[crazymofo]

i hope this helps some





**broken link removed**

 

[jpanhalt]

The "555," actually LM555 or NE555, is an integrated circuit. It is not a microprocessor. However, it can be configured as a non-retriggerable monostable, which will probably do what you want to do. You can go solid state or use a relay to do the heavy work and let the 555 control the time. As I read your description, you just want a driver-controlled mis for your ignition. Right?

John

 

[crazymofo]

hi john,

yes thats right, a miss in the running of the ignition will unload the gearbox in order to do a clutchless gearchange. generally a miss of 65 milliseconds is long enough to acheive this.

one thing i had just thought about, i was thinking of using the side stand circuit to trigger the system, but the circuit will trigger when it goes open, yet the switch i will use will be a trigger when it closes, so i spose i need to add in a switching relay of sorts?

this is where i really fall down... implementing this on some sort of pcb set up! just got no idea on this part.

 

[alec_t]

the circuit will trigger when it goes open, yet the switch i will use will be a trigger when it closes

Not a problem. We can design around that.
Do you have the spec of your side-stand relay? We need to know (at least approximately) the current draw of the relay coil.

 

[4pyros]

yes thats right, a miss in the running of the ignition will unload the gearbox in order to do a clutchless gearchange. generally a miss of 65 milliseconds is long enough to acheive this

Can you buy these?
If so it may give more to go on.
Please provide a link to one if you can.

 

[cowboybob]

First of all, please note:

This is the normal ignition coil wiring scheme. (The transistor switch could also be in the ground leg of the primary of the ignition coil)

The schematic you provided (presumably from the manufacturer) is incorrectly wired.

That said, it strikes me that it would be easiest to interrupt the CKP sensor's signal, with a 555 circuit as you suggest, using a transistor switch ( no "bounce").

There are, however, some timing issues that you'll have to consider:

1. if you interrupt (as suggested above and by an obviously random button push trigger), the spark trigger or for that matter, the spark itself, there may still be a combustion sequence in the cylinder if the interruption occurs after the spark sequence has started.
2. this will affect the "unloading" of the gearbox, thus interferring with the shift process.
3. as a result, you'll have to arrive at a method that is timed to interrupt the spark just before the spark is initiated (by whatever method).

Of course, even just a lessening of the energy of a combustion stroke may be sufficient to achieve the unloading of torque you seek.

(BTW, "The Worlds' Fastest Indian" is a fav movie of mine...)

 

[jpanhalt]

I had thoughts along the same lines and did a quick calculation. 65 msec is the time for one revolution at 1000 rpm. The SV650 is a V-twin 4 stroker, and I assumed he was shifting at a much higher rpm than 1000. So, he may miss the correct timing for the first firing (i.e., hit it right after the spark), but will be OK for the next few strokes. Worse case, he interrupts for a little longer time.

John

 

[crazymofo]

Not a problem. We can design around that.
Do you have the spec of your side-stand relay? We need to know (at least approximately) the current draw of the relay coil.

I can most likely pull the unit from the bike, I presume there will be some numbers on the unit. I do have a multi meter, but not sure how to accurately test the relay with it..

there are commercially available kits, but run between AUD$350-600 for it. Im certain theres not that much worth of circuitry in making one of these lol! Im a racer on a tight budget that i'd much prefer to invest that kind of coin elseware on the bike, and take the time to make something and learn something new in the process.

From what I know from commercially available kits, when you activate the spark kill, it happens instantly, weather or not that falls on a spark event, I don't know, but most kits are adjustable. Ive run commercial ones in the past on other racebikes and generally found 65ms is a good kill time.

thanks so much for the input thus far guys!

 

[crazymofo]

First of all, please note:View attachment 82682 This is the normal ignition coil wiring scheme. (The transistor switch could also be in the ground leg of the primary of the ignition coil)

The schematic you provided (presumably from the manufacturer) is incorrectly wired.

That said, it strikes me that it would be easiest to interrupt the CKP sensor's signal, with a 555 circuit as you suggest, using a transistor switch ( no "bounce").

There are, however, some timing issues that you'll have to consider:

1. if you interrupt (as suggested above and by an obviously random button push trigger), the spark trigger or for that matter, the spark itself, there may still be a combustion sequence in the cylinder if the interruption occurs after the spark sequence has started.
2. this will affect the "unloading" of the gearbox, thus interferring with the shift process.
3. as a result, you'll have to arrive at a method that is timed to interrupt the spark just before the spark is initiated (by whatever method).

Of course, even just a lessening of the energy of a combustion stroke may be sufficient to achieve the unloading of torque you seek.

(BTW, "The Worlds' Fastest Indian" is a fav movie of mine...)

love the words fastest indian, its a fave of mine too!

I seem to remember the ingnition system switches ground to create the spark events for the coils? the coils have constant power to them and the ground switches to create the spark on/off? I could be wrong though as I only read about this a few moons ago.

 

[4pyros]

Im certain theres not that much worth of circuitry in making one of these lol!

3. as a result, you'll have to arrive at a method that is timed to interrupt the spark just before the spark is initiated (by whatever method).

I wonder if the commercial units sense the spark to time the kill.

 

[crazymofo]

I did some searching on these boards and found a couple of threads that covered this, but nothing to actually confirm things. but I found this

this is close to what you want. sorry for the semi-ugly schematic. I've never figured out to draw clean ones using the 555. I set up the relay to break the connection but you can do what you want there. Pulse width and frequency are adjustable. I didn't know how clean your 12V source is so I added a 220uF and 100nF caps. I put a diode in series with the 12V source to protect against battery reversal. R1 controls pulse width, R2 controls frequency. I'd use small trimmer pots. R3 and R4 are optional but are there to avoid running the trimmers to 0. I would find a sealed 12V relay with coil current below 50 mA or so. The switch simply switches power to the unit so it is only drawing current when you use it.
On the relay, you should not switch the ignition coil current.

he also attached a file which ive re-attached. would this be a good starting point for what im attempting to do?

 

[4pyros]

I did some searching on these boards and found a couple of threads that covered this, but nothing to actually confirm things. but I found this



he also attached a file which ive re-attached. would this be a good starting point for what im attempting to do?

Well you would need to keep 555 powered to finish your 65ms and trigger the timer directly.
I dont know if a relay would be fast enough for your timing cycles, you can check some data sheets.

 

[cowboybob]

I took the liberty of modifying your attached schematic (see below).
I used a 555 template that mirrors an actual footprint for that chip (makes it easier to wire up).

Note that I moved C1 to the input of the KILL switch. This is to prevent the 220U cap from continuing to provide power to the KILL circuit (before fully discharging) and possibly prevent a re-trigger when shifting gears very rapidly (especially when down-shifting).

I also simplified the circuit somewhat, particularly in the pulse duration section. There is also no need for frequency control.

Note the closure and release durations of the suggested relay (they are not a concern). You can find the datasheet specs by googling "QUAZ-SS-112D".

 

[WTP Pepper]

First of all, please note:View attachment 82682 This is the normal ignition coil wiring scheme. (The transistor switch could also be in the ground leg of the primary of the ignition coil)

The schematic you provided (presumably from the manufacturer) is incorrectly wired.

That said, it strikes me that it would be easiest to interrupt the CKP sensor's signal, with a 555 circuit as you suggest, using a transistor switch ( no "bounce").

There are, however, some timing issues that you'll have to consider:

1. if you interrupt (as suggested above and by an obviously random button push trigger), the spark trigger or for that matter, the spark itself, there may still be a combustion sequence in the cylinder if the interruption occurs after the spark sequence has started.
2. this will affect the "unloading" of the gearbox, thus interferring with the shift process.
3. as a result, you'll have to arrive at a method that is timed to interrupt the spark just before the spark is initiated (by whatever method).

Of course, even just a lessening of the energy of a combustion stroke may be sufficient to achieve the unloading of torque you seek.

(BTW, "The Worlds' Fastest Indian" is a fav movie of mine...)

I suspect that circuit will blow the transistor. The reverse voltage on the emitter will be high.

 

[cowboybob]

I suspect that circuit will blow the transistor. The reverse voltage on the emitter will be high.

All depends on what transistor you use.

The real point of the proffered schematic was to point out the wiring inaccuracies of the manufacurer's schematic.

 

[WTP Pepper]

Regardless of what transistor you use, it's bad practice. The reverse Vbe could be hundreds of volts and few transistors could cope with that.

 

[4pyros]

I took the liberty of modifying your attached schematic (see below).
I used a 555 template that mirrors an actual footprint for that chip (makes it easier to wire up).

Note that I moved C1 to the input of the KILL switch. This is to prevent the 220U cap from continuing to provide power to the KILL circuit (before fully discharging) and possibly prevent a re-trigger when shifting gears very rapidly (especially when down-shifting).

I also simplified the circuit somewhat, particularly in the pulse duration section. There is also no need for frequency control.

Note the closure and release durations of the suggested relay (they are not a concern). You can find the datasheet specs by googling "QUAZ-SS-112D".

How will it finish the 65ms kill time if the button is released sooner?

 

[cowboybob]

How will it finish the 65ms kill time if the button is released sooner?

I've tried to press and release a button as fast as possible and the best I can do about 85ms.

That's not to say that quicker can't be done. But, as it is, given widely varying shifting cycles and racing conditions, the user will have to "learn' the best button press duration for the conditions at that time.

My main concern was for down-shifting (high gear to lower gears) which is generally done much faster than up-shifting. My observation was that with the 220uF filtering cap maintaining the Vcc (100's of ms in SIM), the circuit couldn't "cycle" down quickly enough to be at a state that would allow another pulse generation in a tight sequence. A fixed, self triggering one-shot 555 isn't the fastest at recovery by gradual power lose. The filtering advantages were maintained.

Now, admittedly, a more sophisticated digital circuit could do a better job, but the OP seemed to be after a "quick and dirty and cheap" solution, so...

 

[4pyros]

I've tried to press and release a button as fast as possible and the best I can do about 85ms.

That's not to say that quicker can't be done. But, as it is, given widely varying shifting cycles and racing conditions, the user will have to "learn' the best button press duration for the conditions at that time.

My main concern was for down-shifting (high gear to lower gears) which is generally done much faster than up-shifting. My observation was that with the 220uF filtering cap maintaining the Vcc (100's of ms in SIM), the circuit couldn't "cycle" down quickly enough to be at a state that would allow another pulse generation in a tight sequence. A fixed, self triggering one-shot 555 isn't the fastest at recovery by gradual power lose. The filtering advantages were maintained.

Now, admittedly, a more sophisticated digital circuit could do a better job, but the OP seemed to be after a "quick and dirty and cheap" solution, so...

All right makes sense. 85ms is your best, bet I could do 75ms. LOL