what is the cable length that runs from the control head to the relay box as i have been unable to find the length on the spec sheet TIA
question on soundoff ETCPMP801
- Thread starter 94yj
- Start date
RS485
Supporting Donor
Are you asking what's the maximum cable distance between a switch-box and Control Point (wccp)?
Sounds like a good question to send to Whelen support!
My short answer: likely not worth worrying about.
Longer explanation:
I did an experiment - I connected a wccp to a freedom lightbar, programmed it so wccp input #1 would flash on a corner lighthead.
I applied voltage (just as a switch would) to wccp input pin #1. I then backed the power supply voltage down the the point where the flashing lighthead was visibly diminished in brightness...this was at ~8.6 volts.
I then inserted a 100 ohm resistor between the wccp pin #1 and the 8.6 V applied to activate it. It _still_ worked. I then substituted the 100 ohm resistor with a 270 ohm resistor. That did _not_ work.
The point of this experiment was to objectively observe an extreme necessary to cause a switching failure and (hopefully) get a sense of how far this condition is from the typical real-world use-case.
So far as the wccp was concerned, that 100 ohm resistance could have been the voltage loss over 8000 ft of 20 gauge wire at 167 degrees F. See table here:
As far as the maximum distance between the wccp and the lightbar, that's pure "CANbus" (which is what "WeCan" is based on).
Maximum CANbus networks distance is a function of operating speed. It's been my experience Whelen runs WeCan at 125kbps.
According to:
maximum network distance is 500m for 125kbps (1640 ft).
Regarding the ETCPMP801:
It says, "Eight switch control panel with three 10 amp and five 0.2 amp outputs for auxiliary device power or function activation" -- you should have no problem using it to signal inputs on the "wccp".
Hope this helps
Sounds like a good question to send to Whelen support!
My short answer: likely not worth worrying about.
Longer explanation:
I did an experiment - I connected a wccp to a freedom lightbar, programmed it so wccp input #1 would flash on a corner lighthead.
I applied voltage (just as a switch would) to wccp input pin #1. I then backed the power supply voltage down the the point where the flashing lighthead was visibly diminished in brightness...this was at ~8.6 volts.
I then inserted a 100 ohm resistor between the wccp pin #1 and the 8.6 V applied to activate it. It _still_ worked. I then substituted the 100 ohm resistor with a 270 ohm resistor. That did _not_ work.
The point of this experiment was to objectively observe an extreme necessary to cause a switching failure and (hopefully) get a sense of how far this condition is from the typical real-world use-case.
So far as the wccp was concerned, that 100 ohm resistance could have been the voltage loss over 8000 ft of 20 gauge wire at 167 degrees F. See table here:
Table of equivalent AWG Wire and Resistance per foot
AWG Chart of Approximate equivalent Cross-Sections of Wire, American Wire Gauge by Resistance per 1000 feet
www.interfacebus.com
As far as the maximum distance between the wccp and the lightbar, that's pure "CANbus" (which is what "WeCan" is based on).
Maximum CANbus networks distance is a function of operating speed. It's been my experience Whelen runs WeCan at 125kbps.
According to:
CAN Bus Protocol and Design Standards | Sierra Circuits
CAN bus broadcasts small messages to the entire network within a concise span through a two-wired bus without involving a host computer.
www.protoexpress.com
Regarding the ETCPMP801:
It says, "Eight switch control panel with three 10 amp and five 0.2 amp outputs for auxiliary device power or function activation" -- you should have no problem using it to signal inputs on the "wccp".
Hope this helps
