CB-1 Electrical Characteristics

[Espeelark]

I searched on this topic prior to starting a new post and there doesn't seem to be any info on the forum available about the electrical characteristics of the CB-1.

The reason for inquiring is that  I have a couple friends assisting with the build of my layout (SP Lordsburg Sub) and we are installing separate blocks that are wired so that train detection can be installed later for a working signal (semaphore) system.
One of my friends (PhD Electrical Engineer) is designing a circuit to detect occupancy within a given block and then output a signal accordingly. His circuit employs an opto-isolator. Yesterday, when he tested the circuit it worked just fine until he performed a short-circuit test wherein it stopped working. We were watching the CB-1 and the LED never turned red indicating a short. So, he replaced the chip containing the opto-isolator and repeated the short-circuit test again, but this time he only momentarily tapped the rail to create the short. Same results: his circuit stopped working and we never saw the LED change to red on the CB-1. We concluded that the chip containing the opto-isolator can’t handle the amount of amperage going through it from a short and it’s blowing before the CB-1 even registers the short.

To change/improve the design of his detection circuit, he would like to know what value (amperage?) the CB-1 has to see for it to determine a short exists and trips the breaker. Also, is that an instantaneous value? Or does it also have to see a defined rate of change?

Can anyone help in this area? Either by having the actual values or having backed into them by t'shooting something similar?

Thanks in advance!
P.S. I've also sent an inquiry directly to Ring Engineering.

Paul Mac

[gregeusa]

Tell your PHD to use a current shunt to protect the opto..

My suggestion is based on the fact that you imply that all the power to the track is going through the opto, not good.

Greg

[G8B4Life]

I don't think anyone here knows the rating for the CB-1 as it's just another fine example of Ring not putting pertinent information about his products specifications in his product manuals; and your the first person that I know of to ask. I'd like to offer a guess but Ring has done some weird things before so if I said 4A it'd probably be 3A for some strange reason. It may even come down to how Ring's detecting a short as well.

However... as Greg said it sounds like your powering the opto coupler by running the track power through it. Without some fancy bypasses, like a shunt as Greg suggested, it won't last long powering it that way. I'd be interested to see how your friends circuit works.

Another thing that should be bought up, have you actually tested the CB-1 by creating a short without the detector in place? I'm guessing that you do know this but to be on the safe side if the CB-1 isn't close enough to the short it may not even see it, so make sure the CB-1 is as close to the bus for that section as possible and not say at the power supply with dozens of feet of wire between the CB-1 and the section bus.

- Tim

[Espeelark]

Hey Greg - my PHD is quite the pragmatic type and likes to keep things simple. We had a couple volt-meters going during the testing and gleaned voltage and amperage to see what was transpiring. Granted this was a very simplistic means of acquiring data, but it was enough to help us characterize what was going on. And yes, all the power was going through the opto...
He mentioned a couple re-design options, and one was a current shunt. He's a Kanoodler and I have no worries he will eventually come up with a robust design solution.

Tim - yes - we did create a dead-short without the detector in place and the CB-1 worked as designed. The CB-1 for this section of track is probably 12-15 feet away from this section's bus. I can always move the CB-1 if needed, but for now I'm going to leave it where its at and see if we can lick this problem.

Ring Engineering did reply (same-day response) and said the following:

"The CB-1 needs to see approximately more than 3 amps before it will trip. The CB-1 is solid state and the trip time is very short.  Something like a few milliseconds."

I'll update this to let you know how things go and what we eventually settle on.

[gregeusa]

My PHD is the opposite, all kinds of complexity and experimentation, I have trouble keeping him to simple ha ha!

He would have used a scope in one shot mode to see the current waveform and precisely see the peak current over time.

No meter is going to give you a good idea at all for something like this, but different strokes for different folks, mine is more in the RF side, and that stuff is black magic, ask any electrical engineer.

Anyway, it sure seems you will have no choice.

Greg