SDS200 Wiring Harness to Linear Power Supply

[srletend]

I've read the previous posts about the red/orange/black wires on the SDS200 wiring harness. I understand the orange wire does not need to be connected to anything unless you want to use the dimmer functionality. The previous posts also make reference to connecting the red wire to positive and the black wire to ground (auto body chassis) in an auto installation.

I'm planning to connect the wiring harness to my Astron 13.8v linear power supply. I'll leave the orange wire unconnected. Red will go to positive. The thing I wanted to double-check was that the black wire will go to the negative terminal on the power supply, not the ground screw. I'm pretty sure this is correct, but for some reason I'm having some brain fog and wanting to confirm...

Anybody with experience using the SDS200 wiring harness red/black to positive/negative on a power supply?

 

[RandyKuff]

Correct... Black to the negative terminal...
The other is just a chassis ground of the power supply...

 

[jonwienke]

Black goes to negative. Negative may or may not be connected to the ground of the power supply.

 

[nessnet]

Anytime you are using a AC to XVDC power supply - always connect + to + and - to -.
Red to red and black to black.

 

[ofd8001]

And to the extent possible, instead of grounding to the chassis, try to run the ground to the negative terminal of the battery.

I don't know much about that specific power supply, but if other things use it too, be sure they do not drag down the output voltage enough to cause the scanner to re-boot.

 

[jonwienke]

We're not talking vehicle installation here, so that doesn't apply.

 

[JoeBearcat]

And to the extent possible, instead of grounding to the chassis, try to run the ground to the negative terminal of the battery.

I don't know much about that specific power supply, but if other things use it too, be sure they do not drag down the output voltage enough to cause the scanner to re-boot.

Usually I refrain from getting into these types of discussions, but I feel I must point out running a device directly to the battery negative terminal is very bad idea. In the past I have seen what happens to radios installed like this when they lose the chassis ground to the battery. ALL the vehicle current runs through the radio (or scanner in this case). Well, it does until something in the scanner acts like a fuse and burns - especially if you do not have the negative lead fused.

I've even seen installs cause vehicle fires using this method - for this exact reason.

Ground to the ground block near the battery and never to the battery negative terminal itself.

Note this post is my personal experience and not that of Uniden.

 

[cmdrwill]

running a device directly to the battery negative terminal is very bad idea.

Exactly, we found out this way back in the 70's. Even tho the radio had a long Negative power cable, the Negative lead was always grounded to the car body near the radio. Even the big high power radios, still grounded right next to the radio unit.

Had one installation, high power UHF radio, radio in the trunk and the 20 foot "ground" negative and positive cables coiled up under the right front passenger floor mat catch the carpet on fire. Why the fire, the negative battery cable came loose, and the high current from the starter used the radio negative 10 gauge cable. And the antenna coax was also burned. Two way radio sales man's company car.

 

[freqseeker]

Well, it does until something in the scanner acts like a fuse and burns - especially if you do not have the negative lead fused.

The key here is you should always fuse the negative lead. This step is skipped all the time.
As for grounding to the dash there can be problems with this. Modern cars have very little metal to ground to. With scanners you should be fine, but two way radios should go to the battery.
U joints used to go bad from poor grounding causing arc pitting.
Grounds cause a lot of problems in vehicles. Having worked in auto repair nearly forty years I have definately seen more failed grounds vs power circuits.

 

[W4EMS]

Also some recent models (such as Nissan) the vehicle computer adjusts the charging. Going directly to the battery negative terminal affects this process. The manual (or dealer) can show you the ground lug terminal on the chassis to attach the ground. And as mentioned before seems like a good idea to fuse the ground line too. But loosing a chassis ground seems to be rare.

 

[ofd8001]

Here is what Motorola and Ford got to say:

Motorola Radius CM 300 Installation guide:

Connect the black lead of the power cable to the nearest vehicle chassis ground point, which is
usually the central ground point near the battery (using the provided ring lug if necessary).
Shorten the black lead to remove any excess cable. (See Figure 2-2.)

Ford Modifier's guide:

Equipment Grounding Guidelines
• Do not ground the body to the transmission or transmission crossmember. Ground accessories to the chassis or the vehicle battery.
• Splicing into circuitry relating to the electronic engine and/or transmission control systems is not acceptable because of the adverse effect
on the electronic system operation.

2020 Police Interceptor Utility and Hybrid Utility Modifiers Guide, 5/2020

I'm concerned that someone will think a metal piece inside the passenger compartment is considered a chassis ground, "because, after all the passenger compartment is connected to the chassis" which has its fallacies.