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DaveAK
16 September 2010, 1246
So, I'm hoping to wire up my bike this weekend, but during my morning deep thinking time, (when I shower!), I realized that my ignition circuit isn't failsafe, i.e. it will fail on rather than fail off. Bummer. Still, I'm going to stick with it for now and just say that I got the design from Toyota. :D

The idea was to use the gate pin on the Vicor DC-DC converter to control the 12V to the relay that feeds the contactor. This works by switching off the output when the gate is grounded. Which means that if the switch fails, or the circuit is broken the 12V will become live. Doesn't mean that my bike will go up in smoke or disappear in to the distance without me, but it is poor design, and we don't like that, do we?

So, something to add to the list of rework items for this winter. I just hope that I can get one ride up and down the driveway before the snow comes. :)

ZoomSmith
16 September 2010, 1304
Be sure and get some video Dave. If this is your "Frankenstein" run, it's is a real milestone for the projoect.

BTW, funny how your ideas hit in shower, than's my time/place too. What's up with that

EZwryder
16 September 2010, 1310
Hey Dave,

Saw you were back on the board, good to hear from you. I was off for a while and away for the summer, so I've only turned back to my project in the last couple of weeks. However, I have made enough progress to get it rolling, which has made it easier to contemplate the ever-growing list of things to change and improve.

We had a big discussion about emergency disconnects and contact ratings for high DC voltage circuits, so I have been looking about for these quite a bit. Many can handle the amps, but not the V. I stumbled across this one last night from Chennic. I have their DC-DC converter and a charger. Haven't asked about the cost for this unit, but I do see it's rated for 80V and 250 amps continuous.

http://www.chennic.com/show-products.asp?id=85&JCEDS

Regards,

Dale

frodus
16 September 2010, 1333
hey dave, use a NC contact on a relay, and a very small aux battery. That way, if anything fails, the relay disengages and closes the contacts, closing the circuit.

Also, the DC-DC itself shouldn't be what turns on the Contactor, there should be something controlling the 12V effectively.... like another auto relay in there.

DaveAK
16 September 2010, 1344
hey dave, use a NC contact on a relay, and a very small aux battery. That way, if anything fails, the relay disengages and closes the contacts, closing the circuit.

Also, the DC-DC itself shouldn't be what turns on the Contactor, there should be something controlling the 12V effectively.... like another auto relay in there.
This setup was to avoid the use of an auxillary battery, and seemed like a good idea at the time. Apart from the flaw of it not being failsafe, I think it was a good idea. I'm still going to go with it for now, and then I'll either consider a small battery or capacitor like Bruce went with, unless I can come up with something else. And I will have a relay in the circuit. It's sitting on my desk at home as a constant reminder that I've got work to do, (someday).