roberttroll wrote:Sorry - that is for the true value XO rust line.
The biggest issue i have with getting the Curtis to work is coming up with a design that is fail-safe. That is finding a way that the armature will never receive power if the field does not. As it stands now, in my design, there is a possibility of that happening if the relay that i am using fails in the closed position. So i have put in idiot lights. Now i have asked quite a few people the question "what are the chances that a normally open relay fails in the closed position." I kind of get stares and not much in the way of an answer. I just want something that is 99.999%. My design number 3, uses STDP relays. Those are impossible to find in stock in 36v. So i have to use 24v ones which i am not crazy about......
I was also reminded that there is nothing in the original GE design that prevents the scenario (armature power - field no power). So it most likely inst a catastrophic situation.
Robaroni wrote:On relays: Actually locking in the closed position is quite common. Here's why. Relay pit if there's the slightest impurities on the contacts, dust, oil, etc. And when that happens they can 'lock' in the on position because the pits on each contact 'lock' to each other, so you're right to be concerned. The other thing about relays is that if they are adjusted correctly there is something called 'follow' that must take place. Follow happens when the contacts meet and continue for a short period so as too clean the carbon or other impurity off. So check your relay's to make sure they have follow as it will extend their life considerably.
Also, I'm wondering if the Curtis has a lead extended out so that you can shut it off automatically if the state is wrong just for conditions like you had or something catastrophic occurs? this may be a way to reslove your problem using a simple sensing circuit.
roberttroll wrote:I hope all that makes sense. My background is not in electronics and i have learned by experimentation and pulling things apart.
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