LCS Sensor Transmission Terminator

Not to worried about it. They'll send them out for free and you only need 1. But curiosity is a good thing. I'd have to look harder at it or just see if Rudy posts. 

Thanks for the reply, it's all curiosity at this time. The cap is definitely connected to power supply common on one side (now that I look at the cable better), and the pin on the cable next to it that doesn't go to the DB9. Or it may go over one pin to the Transmitted data pin.

I'm at 62 feet of cable with 6 sensors. All works fine. I tested the sensors briefly before I installed them .

Inquiring minds, eh?

It's a tantalum cap from the looks of it.  Hard to tell in those shots.  Can you read the value on the cab and tell which pins it's connected to?

I must have missed something.

 

This thread is the first I have heard of an LCS transmission terminator.  What is its purpose?  Is it necessary?  It reminds me of the old SCSI terminators.

 

My LCS configuration includes the WiFi module, 3 sensor tracks and 2 ASC2's, and everything seems to be working.

First I've heard of it as well, that's why I'm curious.

 

It solves an issue where sometimes the record function of the sensor track will drop out of the "recording armed" state. If all is working you don't need it. I found it by accident by using a different length cable between a few components. 

Hmm...  I've seen that as well, and I only have two sensor tracks connected.  Maybe I should build one of these and try it if I could find out what value and what pins that cap is connected to.

 

Here is some interesting backstory... when developing the High Rail SensorTrack recording feature, I noticed that a SensorTrack would not always remain in the "armed" state. A SensorTrack would transition from the "armed" state (red light is blinking) to "idle" (red light stops blinking) for no apparent reason. It would sometimes take a second or so, or even minutes for the issue to occur. I spent countless hours trying to determine the cause from the perspective of High Rail. I thought High Rail must be sending a "junk" message, or doing something goofy. But it turns out that is not the case. The issue is noise from other activity on the PDI bus, which forces the SensorTrack out of the "armed to record" state. You can duplicate the noise issue using a CAB2 remote and a little patience. So why did High Rail expose the issue? It's because High Rail must constantly ask an "armed to record" SensorTrack for its status in order to keep High Rail synchronized with the SensorTrack's current state. That extra bit of traffic from the "keep me in sync" commands apparently causes enough "noise" to disarm a SensorTrack (but not always, which is frustrating). Railsounds and I spoke at length about the issue. Within a short period of time a "terminator" showed up in the mail from Railsounds. All is well. 

 

The images posted by cjack are from the High Rail post regarding this issue. 

 

I can't post a link to the High Rail web site (because I am not an advertiser). However, if you tap this Google search link, then you'll get there faster. I don't think adding a Google link is against the rules (we'll find out).

 

https://www.google.com/webhp?g...sl#q=highrailcompany

I just want to know how to fabricate it, it looks very simple, and I have the connectors.

 

Oh sorry Brian, I should have thought to note where I got those pictures. My bad. And thanks for them too.

I'll see if I can get the value tonight.

Thanks Marty, and the pins and polarity too.  If it's a tantalum cap, it has a polarity.

 

I thought tantalum but I've had some cer like that...
I was wondering what that unused pin was for.
Almost looks like it's connected to that and com.

 

John. 

 

This is is the best shot I could get. It's either 103 or 108. Im leaning to 103. What do you think?

 

 

 

 

I think it's 103, most likely a ceramic capacitor. Can you tell which pins it is soldered to?

 

 

 

 

Cjack that what I thought, .01uf. Couldn't tell for sure if it was an 03 or 08. 

 

 

Well that definitely looks like it is across the fifth and fourth pin on the connector. And the fifth pin connects to pin #5 on the Base DB9. The fourth pin does not connect to the Base. Someone want to check that I have it correct?

I would have to take a sensor track apart to see what that pin does connect to. Maybe we don't need to know...just use it. Curious though.

 

It could be that there is a terminator inside the sensor tracks as part of the circuit. And when you plug in a .01uF to the last port connecting pin 4 to pin 5 which is COM, it puts the terminator in circuit at the end of the transmission line.

Big guess...

It cetainly has to be a 103 vs a 108, a 108 would be a 1000uf cap, and be a ton larger!

 

A 103 would make more sense if it's on a signal line, it's probably a noise filter.  It looks like only the last two positions have contacts, which would certainly suggest where it's connected.

 

 

More mystery...the pin #4 is labeled on the sensor circuit board as PORT. So the cap connects the COM to PORT with .01uF.

BTW, what's the purpose of the short yellow wire just sticking out?

 

 

Chuck, the spike filter function would explain why they have it going from common to a data pin.

My guess is help remove it. I can't see any reason for it. Not the best handle in the world. 

I think it is more likely a transmission line termination. To prevent reflections of the data transmission line. I have no evidence, but it is a known technique that terminating a transmission line in a device like this can be a part of the device circuit board and a jumper or maybe this capacitor in the last unused port can put it in use.

I'd expect a terminator to also have some resistance, but who knows.  Since I don't really know the characteristics of the signal on that pin, it's hard to say.

 

Yes, and it may already be on the boards I thought. Maybe a 120 ohm like the characteristic impedance of a similar size pair of wires. Then it could be connected with a simple jumper. Or a capacitor...but why a capacitor, that's part of the mystery. not as handy in the field as a jumper wire.

Time for someone like Jon Z. to chime in and tell us the real story.