Tiny gauge wire for 5v sensors ok?

General support questions and announcements for MS3. See also MS3 manuals.

Moderators: jsmcortina, muythaibxr

Tiny gauge wire for 5v sensors ok?

Postby forcefed86 » Fri Apr 21, 2017 5:50 am

Working on an MS3 setup. Already have some RCA cables running the length of the car and I’d like to run a couple 5v pressure sensors in the trunk area off them. The wire gauge on these RCA connectors is TINY. I’d guess 22-24g? Is there any real amperage requirement on a pressure sensor? I was going to run the 5v supply and sensor input off the 2 wires in each RCA cable and ground in the rear.
forcefed86
Helpful MS/Extra'er
 
Posts: 128
Joined: Wed Aug 13, 2014 7:08 pm

Re: Tiny gauge wire for 5v sensors ok?

Postby Matt Cramer » Fri Apr 21, 2017 6:25 am

I'd be worried about ground offset problems unless you ran the ground to the ECU.

22 to 24 gauge wires have very little mechanical strength; they're easily broken if you accidentally pull on them. But the current is in the milliamp range, so you're not going to burn the wires out.
Matt Cramer
Super MS/Extra'er
 
Posts: 13158
Joined: Thu Apr 16, 2009 8:08 pm

Re: Tiny gauge wire for 5v sensors ok?

Postby forcefed86 » Fri Apr 21, 2017 6:35 am

They are very similar to this. 2 tiny wires per cable and encased in a thick rubber. I don’t think the wire breaking would be an issue unless it was at the terminal. I have 4 tiny wires I could work with. I had planned on combining the 2 wires per L/R RCA cable for a little more strength for the 5v and signal. I guess I could dedicate one wire to a shared ground up to the ECU if that would work best?

Image


Thanks!
forcefed86
Helpful MS/Extra'er
 
Posts: 128
Joined: Wed Aug 13, 2014 7:08 pm

Re: Tiny gauge wire for 5v sensors ok?

Postby DaveEFI » Fri Apr 21, 2017 6:48 am

Very odd RCA cable.It's normally a co-ax cable, designed for unbalanced audio, etc.
Rover SD1 3.5 EFI
MS2 V3
EDIS
Tech Edge O2
London UK.
DaveEFI
Super MS/Extra'er
 
Posts: 2401
Joined: Sun Apr 15, 2012 12:55 am

Re: Tiny gauge wire for 5v sensors ok?

Postby forcefed86 » Fri Apr 21, 2017 6:52 am

DaveEFI wrote:Very odd RCA cable.It's normally a co-ax cable, designed for unbalanced audio, etc.


I believe they are just to carry the sub signal from the head unit to an Amplifier. Then you use the monster wire from the amp to the speakers.
forcefed86
Helpful MS/Extra'er
 
Posts: 128
Joined: Wed Aug 13, 2014 7:08 pm

Re: Tiny gauge wire for 5v sensors ok?

Postby billr » Fri Apr 21, 2017 7:55 am

That non-coax config isn't odd in the USA. The RCA/phono connector has been used in countless different ways since the '40s; with simple parallel wires, twisted-pair, and coax. There really is no standard for an RCA "cable", only the connectors.

PS: in this application I would be worried about the lack of shielding.
billr
Super MS/Extra'er
 
Posts: 4077
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Tiny gauge wire for 5v sensors ok?

Postby forcefed86 » Fri Apr 21, 2017 9:34 am

You’d think an audio cable would be sensitive that sort of thing. But I suppose if it’s a bad idea in general I can just zip tie some real wires to the RCA cable pull it through the chassis under the carpet.

Thanks for the opinions. The easiest route never seems to be the best!
forcefed86
Helpful MS/Extra'er
 
Posts: 128
Joined: Wed Aug 13, 2014 7:08 pm

Re: Tiny gauge wire for 5v sensors ok?

Postby billr » Fri Apr 21, 2017 9:52 am

It depends what you mean by "audio cable". In the detection or pre-amp areas the signals can be fairly low/high-impedance and sensitive to EMI; but the output to speakers is often very low-impedance and quite immune to EMI.
billr
Super MS/Extra'er
 
Posts: 4077
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Tiny gauge wire for 5v sensors ok?

Postby Six_Shooter » Sat Apr 22, 2017 5:21 am

Twisted pair cables are better at noise rejection (noise cancelling to be technical) than co-ax based cables. I've installed car audio since the early '90's and the best cables I've used have been twisted pair, sometimes I've made them myself with some 18AWG trigger wire. Usually unshielded twisted pair works better for noise rejection than shielded, in my experience.

That being said, I'm not sure I'd use RCAs for the sensor connections, not because I think there'd be any issue with the signal, though as suggested the 5V reference and ground connections need to be made to the ECU, but simply because i'd prefer to just run new dedicated wires for the sensors.
Last edited by Six_Shooter on Sun Apr 23, 2017 6:39 am, edited 1 time in total.
Tha Toy: 1973 Datsun 240Z Turbocharged, and loads of fun, now MS'd
Tha Otha Toy: 1923 T-bucket Hot Rod, Yes, it's MS'd
Tha Daily: 2000 GMC Yukon, not so fun
Tha Long Term Project: 1985 GMC S-10 Jimmy, hasn't been fun for a while
Six_Shooter
Experienced MS/Extra'er
 
Posts: 336
Joined: Mon Oct 17, 2011 7:28 pm
Location: South Western Ontario

Re: Tiny gauge wire for 5v sensors ok?

Postby DLRacing » Sun Apr 23, 2017 12:52 am

Twisted pair should work fine as far as EMI pickup is concerned, IF you use each pair for the signal and ground.

You MAY have acceptable results with using one pair for signal from one sensor, and +5v for both, and the other pair for signal from the other sensor and ground for both.
Use the sensor ground from the ECU in either case.

David
DLRacing
Experienced MS/Extra'er
 
Posts: 159
Joined: Mon Aug 15, 2016 7:48 am

Re: Tiny gauge wire for 5v sensors ok?

Postby billr » Sun Apr 23, 2017 10:30 am

I gotta ask... we keep talking about a 2-wire RCA connector/cable, but a "5V sensor" will require three wires. How is the other wire going to be handled? Yes, twisted-trio wire can be used, but sure won't work nicely with the RCA... Besides, the OP's whole point in using the RCA is because there are already existing RCA cables, which I assume are (existing) 2-wire.

Oops: I just re-read the first post, the OP was going to ground the sensors "remote", in the trunk (to the chassis?). Yeah, that is asking for trouble.
billr
Super MS/Extra'er
 
Posts: 4077
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: Tiny gauge wire for 5v sensors ok?

Postby DLRacing » Sun Apr 23, 2017 10:39 am

billr wrote:I gotta ask... we keep talking about a 2-wire RCA connector/cable, but a "5V sensor" will require three wires. How is the other wire going to be handled? Yes, twisted-trio wire can be used, but sure won't work nicely with the RCA... Besides, the OP's whole point in using the RCA is because there are already existing RCA cables, which I assume are (existing) 2-wire.

Oops: I just re-read the first post, the OP was going to ground the sensors "remote", in the trunk (to the chassis?). Yeah, that is asking for trouble.


The 5v and sensor ground can be shared between more than one sensor. That's exactly how most factory harnesses are wired.
DLRacing
Experienced MS/Extra'er
 
Posts: 159
Joined: Mon Aug 15, 2016 7:48 am

Re: Tiny gauge wire for 5v sensors ok?

Postby billr » Sun Apr 23, 2017 10:50 am

For twisted-pair to be effective the signal and ground for each signal have to be in the same "pair", and the ground for each signal should terminate at the MS. Yes, the 5V can be shared, but not the grounds if you want the best EMI resistance. It all depends how good you want to avoid any possible EMI problems. Like the OEMs, I make compromises in my wiring, but am aware of what I am doing and accept the results.
billr
Super MS/Extra'er
 
Posts: 4077
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA


Return to MS3 General Support

Who is online

Users browsing this forum: TonyR85 and 6 guests