Suggestions - Overload Lockout

[DonTZ125]

I'm just about ready to actually start doing the things I've been muttering about for months now; I'm almost ready to go to alpha prototype on a number of toys including a spark-only SMT variant of the MegaSquirt engine controller - yes, I'm trying to go head-to-head with Ignitech!

One of the first items I want to release will be a voltage overload lockout that chops the power to the TCI if the voltage gets too high. Engine doesn't run, alternator doesn't melt your harness or blow your lights and ignitor. I will offer an internal version for rebuilt TCIs, as well as an external version that plugs into the black box.

I have two questions / requests for input - first, what should the threshold be? I'm thinking around 15.5v, +/- 3%. Second, should this be a 'soft' interrupt that allows the engine back on as soon as the volts drop, or a hard lockout where you have to flip the kill switch to reset? The paranoid side of me says "Kill it hard!", but I can see someone wanting to limp their bike home, lugging the engine low enough that the alternator isn't spinning fast enough to do damage.

Thoughts?

[ragedigital]

Can't you just put a Zener diode in there and limit the voltage through that?

[DonTZ125]

The problem comes in with the amps - too much voltage leads to too many amps leads to a fried zener, at which point the overvoltage starts blowing things up again. Most of the Zeners I've been seeing (other than BIG buggers) are in the 0.5W range, which at 16V is only 31mA. Bear in mind, I'm not just protecting the TCI - I'm also trying to protect the entire electrical system!

[ragedigital]

What kind of amperage are you talking about? The TCI won't be pulling too many amps.

I figured the VR would be supplying a steady voltage for all of the other components outside of the TCI.

[DonTZ125]

Yes, unless the VRR *FAILS*, as it is wont to do...

[apsolus]

i like the idea of a soft engine shut down. seems alitle more user friendnly to me. 15.5 volts sounds good to me. good luck man takes real skill

[yamaha_george]

Don,
Perhaps a thermal sensor? As you say soft hit is good for a rider BUT he would have to KNOW the cut out has switched in by some kind of warning LED or some such.

Hard cut is safest as it takes out the "human element" i.e. stupidity & again there must be some visual given so he does not get home and faff with the carbs or some such.

[thatkid]

I think it's a great idea 15.5V should be fine, I prefer the "limp home" notion.

Regarding Geo's input, "some kind of warning" how about an audible warning? a mini piezo buzzer built into or mounted on the device would that be feasible? something like this http://www.dhwelectronics.com/Piezo_Tra ... cer_Buzzer

[yamaha_george]

I think it's a great idea 15.5V should be fine, I prefer the "limp home" notion.

Regarding Geo's input, "some kind of warning" how about an audible warning? a mini piezo buzzer built into or mounted on the device would that be feasible? something like this http://www.dhwelectronics.com/Piezo_Tra ... cer_Buzzer

Mal,
that had crossed my mind but make the circuitry more complex i.e it would need a source of sound plus a driver where a LED takes less current and in digital cct less components to drive it also less to fail.

The whole thing will require a reset that is NOT easily accessible so that it cannot be reset by some one who just wants to get home and damn the results and then blame Don !! or worse try & sue him.

Don also has to draw up a notice that all of his stuff is used at the bike owners risk so there is NO legal come back if
A} it is mis-wired and then burns the bike.
B} it works just fine but is ignored by the owner and then damage occurs

[DonTZ125]

I thought about an indicator and reset, but the way I want to build it there will be no way for the rider to override it - cross 15.5v, and your engine shuts off. Period. A hard lockout means you have to turn the power to the TCI on and off (kill switch will do), soft kill means the power comes back on when you drop below the threshold. Either way, as soon as you get back up to 15.5v it's going to chop your ignition again. The more I think about it, with a soft interrupt you should be able to ride it home without any extra consideration - it'll effectively have a rev limiter set at whatever engine speed the alternator puts out 15.5v. You'll sound like someone bouncing their engine off the limiter on a dyno (just a lot quieter). The "da-da-da-da-da-da-da" of the engine should act as an audible indicator!

As planned, there will be no wiring to bodge around with or screw up - you unplug the 6-pin connector on the TCI, plug the interrupter into the TCI, plug the stock harness connector into the interrupter. Moron proof. (Can I make it new-R6-racer proof?)

Thoughts?

[olie05]

Personally I wouldn't be interested in this, but then again I haven't had any problems with my charging system up until now.

Why not focus on incorporating this feature into the programmable ignition system you're developing?

It would be a simple logic command at that point.

[DonTZ125]

The fragility of the 4-pin VRR and the damage a dying unit can cause is well documented, here and on the Archives. There has even been one or two cases of new-style VRRs dying and taking pieces with them. I want to make a tool that people can use to protect their bikes.

As to your second point, it would be rather rude (and probably poor business sense) to force people to buy a $200 programmable ignition in order to get the benefits of a $50-75 overload board.

[yamaha_george]

The fragility of the 4-pin VRR and the damage a dying unit can cause is well documented, here and on the Archives. There has even been one or two cases of new-style VRRs dying and taking pieces with them. I want to make a tool that people can use to protect their bikes.

As to your second point, it would be rather rude (and probably poor business sense) to force people to buy a $200 programmable ignition in order to get the benefits of a $50-75 overload board.

Don,
If it was software in the programmable ignition then it would be a good selling "feature" for that system for those of us that would think about such an item for our bike, maybe just enough to tip the balance in your favour , particularly for those of us who have not had problems in that area.

I do understand that for a basic precaution your stand alone protector circuit is sound and cheap enough (compared with catastrophic failure costs ) to be of interest to all but the real cheapskates who believe it will never happen to them.

[olie05]

Maybe I'm just playing devils advocate here, but wouldn't a properly fused harness withstand an over-voltage condition? Again, I've never experienced one of these VR failures myself, so I don't know what pieces it takes along when it fails.

[DonTZ125]

Proper fusing - you'd think so, wouldn't you?? The fact is, a dying VRR will kill: head, tail, and signal lights; signal and safety relays; harness connectors; and most expensively, your TCI (black box / ignitor). Since the coil drivers AREN'T fused, they are the most commonly damaged components - it was actually the idea to repair / replace the fried ignition transistors that was the kernel of this whole business idea.

You're right, it would be quite simple to set up an internal kill switch based on the voltage strength (the battery strength is monitored anyways), but I do want to offer a discrete unit.