There are two connectors on the end of the pressure switch marked C and NC. How do these get wired into the controller so that they can control the pump pressure? Any help appreciated.
Team 1163
The Trojan Horses
C (for Common) and NC (for normally closed) are the two sides of the switch inside. At low pressure, the switch is closed.
Connect the terminals to a ground pin on the DB-25 connector, and to an appropriate digital input pin (it doesn’t matter which of C or NC goes to which of ground or input).
In tyour program, the closed swith appears as a 1, changing to a 0 when the pressure gets near 115 psi. It stays open (0) until the pressure drops to is it 85 psi, then goes to 1, again.
It actually doesn’t matter which way you do the NC and C, from what i’ve tested, because it’s a digital switch anyways.
That sounds great. Thanks for the assistance.
Team 1163
You will need to make a cable that connects into the Digital Input on the controller. We have ours connecting to pins 2 and 6 as labled in the Manual on page 13.
Our team is using this switch, and I have a question…
Do we HAVE to wire it up to the RC thrugh the digital inputs or can we just wire it in series with the compresser. The latter would be 1000 times easer, safer, and save about 5 feet of wire. I just have it:
(12v+) --> (COMMON)
(NC) --> (COMPRESSER +)
(COMPRESSER -) --> (12v GND)
and that seems to work fine, it shuts off at 115 psi and there is no programing required. Did I make a big mistake or is this acceptable? thanks in advance - Jacob
*Originally posted by jacob_dilles *
**Our team is using this switch, and I have a question…Do we HAVE to wire it up to the RC thrugh the digital inputs or can we just wire it in series with the compresser. The latter would be 1000 times easer, safer, and save about 5 feet of wire. I just have it:
(12v+) –> (COMMON)
(NC) –> (COMPRESSER +)
(COMPRESSER -) –> (12v GND)and that seems to work fine, it shuts off at 115 psi and there is no programing required. Did I make a big mistake or is this acceptable? thanks in advance - Jacob **
NO!!! Not only is this specificly prohibited in the rules, it is also dangerous as the switch is not designed to handle the amounts of current that the compressor draws. ALL switches, sensors, etc MUST be wired to the RC; they cannot control motors directly. Likewise, all motors/compressor must be wired to a speed controller or relay.
whoops
If anyone wires the pressure switch to a digital input, they will simply be disqualified. FIRST specifically states in the checklist that the switch must be wired through a RELAY. I guess i’m going to have to make some modifications next week.
*Originally posted by pras870 *
**If anyone wires the pressure switch to a digital input, they will simply be disqualified. FIRST specifically states in the checklist that the switch must be wired through a RELAY. I guess i’m going to have to make some modifications next week.**
No. You must wire the pressure switch to the digital inputs. Then the RC will turn the pump on and off though a relay. You cannot wire the switch directly to the relay, it specificly says so in the rules.
http://www2.usfirst.org/2003comp/2003inspechecklist.pdf
#38
Pressure switch cannot be wired in series with the pump. It must go through a spike relay.
*Originally posted by pras870 *
**http://www2.usfirst.org/2003comp/2003inspechecklist.pdf#38
Pressure switch cannot be wired in series with the pump. It must go through a spike relay. **
Replacing the pronoun with its antecedent, we have:
The compressor must go through a spike.
There are reasons why everything you can do is not something you should do. Maybe the folks at IFI have made sure that First team members are safe from their mistakes, but just because you got away with it, doesn’t end it.
The Spike relay is two circuits in one package. The input is an LED which needs the appropriate current and (thus) the appropriate voltage and polarity.
The pressure switch has no source of 5 V, which is what the Spike needs on its input. If you wired the input, via the pressure switch to +12V, which is the only voltage available (except in your electronics) you could
a) apply overcurrent and blow out the LED input to the Spike, or
b) apply high reverse voltage and blow out the LED input to the Spike, thus ruining the Spike. :ahh:
If you wire the switch to the RC digital input, and put the compressor-controlling Spike on an appropriate output, the Spike is supplied with the design-nominal voltage/current level signal, and the compressor can be officially turned off before and after the match. 
The advantages to doing it this way include not being told to rewire and get re-inspected, and not having erratic (or no) operation of the Spike.
Hope this helps. 