Electrical Help Needed - Power Distribution Box

[cj74]

Been working on a project that has me stumped. Since I my slot car work space is shared with the home office I am trying to reduce desk space that I need. The project... Use one power supply to power a distribution box that has 5 outputs controlled by separate variable switches and metered (Voltage and amps). At this point I can control each output independently, but I’m getting the same voltage on all meters.

Is it even possible to do what I’m trying to do?

CJ

[PetesLightKits]

Best thing to do is list your input and outputs volts and amps. Depending on what your input and outputs are will determine how easy or complex you will need to be. Low power circuits may be able to use basic resistors, whereas higher demand circuits may need transformers and/or transistors with other components to make it all work.

Probably the simplest way would be to buy 5 adjustable voltage regulators, hook them all up to the same input source (in parallel), then adjust and send all your outputs to your different hookup interfaces. You can get cheap voltage regulators on www.dx.com. They work for up to about 2.5 Amps, 3 - 40 Volt input, 1.25 - 35 volt output. What this means is that your input will need to be able to handle 10 Amps (5 x 2.5 Amps).

Peter

[cj74]

Hey Peter,
Thanks for the response. I'm attaching a wiring diagram for what I have now. To the best of my abilities, I'm pretty sure I have it wired up the way you have suggested. To answer your initial question:

Input Source is capable of 3-15V and 25 Amps.
I'd like each output to be capable of up to 12V and up to 2.5 Amps.

I have all the components I need and actually have them wired up as shown in the attachment.

[PetesLightKits]

That schematic looks correct - exactly what I had described. And you are still getting the same voltage across all outputs despite making individual adjustments to each potentiometer? What voltage reading?

Maybe double check the voltage regulator input and output terminals, or maybe try hooking one regulator up at a time, making sure that it is working at reducing your voltage. Remove the VA meters and switches and just hook up the input to the regulator, make some adjustments on the pot and measure with a portable meter at the terminals. Then add components back in, one at a time, doing the same checks until you see something odd.

Peter

[PetesLightKits]

Ah, just noticed this - don't run your output through your volt/amp meters. Run your outputs directly to your hookups and measure output voltage in parallel, not series.

[4424ever]

Thanks Pete I was looking at that dia earlier and couldn’t put my finger on it but something didn’t look right You are 100 % right volts are in parallel and amps in series
CJ keep the power supply for the meters isolated like you have in the dia or the accuracy of the meters will be affected by the regulator output

[cj74]

Ah, just noticed this - don't run your output through your volt/amp meters. Run your outputs directly to your hookups and measure output voltage in parallel, not series.

So my meters will have to be outside the box? I'm trying to keep it clean, like this:

[RichD]

To try and simplify things I drew out just one set. The rocker switches each apply 9 volts to their corresponding display, they do not turn off the voltage regulators, just the displays. The positive and negative inputs of the voltage regulators are connected to the power supply. The plus output of each regulator goes to both its positive terminal and to its corresponding display. The minus output of the voltage regulator goes to the minus input of the display and plus on the display goes to the negative terminal.
I believe that the connections to the display are the problem. The volt meter part of the display needs to be in parallel with the outputs of the regulator and the amp meter needs to be in series, so I think the yellow wire is connected to the wrong place. I believe that the plus output of the voltage regulator needs to go to the plus input of the display and the yellow wire needs to go to the negative terminal.
Try changing just one set! I am keeping my fingers crossed.

[PetesLightKits]

So my meters will have to be outside the box? I'm trying to keep it clean, like this:

No, physically, they can be wherever you want them to be. I modified your schematic - it's a bit crude, I haven't shown the input connections and, obviously the positive wires are not connected to the negative wires. This should at least get you some variation on the voltmeter when you adjust the pot on the regulator.

[cj74]

K. I follow the thought process. The wiring instructions for the meter show the black wire and red wire on the top as being in series. So I was worried about connecting them in parallel (excuse my poor electronic speak, it has been 20 years since I've taken circuits). When both wires are disconnected and everything else is wired up I can get a voltage reading when I touch either to the load negative. I'll give this a shot and report back either later tonight or tomorrow morning.

[cj74]

To try and simplify things I drew out just one set. The rocker switches each apply 9 volts to their corresponding display, they do not turn off the voltage regulators, just the displays. The positive and negative inputs of the voltage regulators are connected to the power supply. The plus output of each regulator goes to both its positive terminal and to its corresponding display. The minus output of the voltage regulator goes to the minus input of the display and plus on the display goes to the negative terminal.
I believe that the connections to the display are the problem. The volt meter part of the display needs to be in parallel with the outputs of the regulator and the amp meter needs to be in series, so I think the yellow wire is connected to the wrong place. I believe that the plus output of the voltage regulator needs to go to the plus input of the display and the yellow wire needs to go to the negative terminal.
Try changing just one set! I am keeping my fingers crossed.

Hey Rich,
Thanks for chiming in. Unfortunately, I got lost in reading this. I'm going to come back to it after I shake off some cobwebs.

[SpeedyNH]

my combination Volt-Ammeters require three connections on the measuring side: the plus side should go in and out through the module from the supply to the track so that current can be measured, and the minus is used as a reference for the Voltage, and also then goes to the track from that same point.

[RichD]

I was too lazy to draw a schematic and in any case I would like to see what the connections on the meter looked like first. If you did what PetesLightKits suggested the amp display would not read.

[PetesLightKits]

Yeah, I know that. I was just trying to break down the problem to its' simplest form to see if there was, at least, some variation in the voltage when the pot was adjusted.

[HO RacePro]

Fully admitting my blind ignorance here...

Is it possible your voltage regulation circuits need to have a load on them before they'll show a reduced voltage? Could it be they'll show the full input voltage at their outputs until there is a load to draw it down?

Ed Bianchi

[cj74]

I'm starting to think the issue is with the internal circuitry of the variable switch.

@PetesLightKits... I'm pretty sure I implemented your suggestion as written. The result was a shorted circuit. The motor stopped turning, the amp reading shot up. Pretty sure I fried the variable switch as well. It was worth a shot and not the first switch I fried.

@RichD... I'm including here the model of the meter (DSN-VC288). I've read quite a few posts/write ups on the switch and I believe that my interpretation regarding placement of the yellow wire is correct.

@HO RacePro... At this point I'm working with informed ignorance and still not successful, so I'll take all the thoughts I can get. The issue isn't that I'm not getting a voltage reading, I'm getting a voltage reading on a portion of the circuit that I shouldn't.


A couple of new realizations this morning. I'm feeding the supply voltage from bottom up. If I turn on a regulator downstream,a all up stream meters read the same voltage as the meter of the regulator I'm turning on. Strangely, the LED on the regulators that are not switched on do not light up. Even stranger... If I turn on a regulator nearest the supply voltage only the meters upstream read, bit the downstream switches indicate power on via the LED.

I may be missing a number of things that are changing along the way, but I'm trying to be conscious of only changing one thing at a time. But, I'm truly thinking my regulator switches may be the issue.

[PetesLightKits]

Sorry about that. I did a quick test using similar equipment, but with only input power supply at about 10 V dc, the voltage regulator with the pot adjusted to 3 V dc output and an LED hooked up to the 3 V dc output. I was able to get a good voltage reading from the + and - of the output side, hooked up in parallel.

Why are you using switches to turn the meters on and off? I would just wire them up directly to your 9 volt supply and not worry about it.

And you also have switches on the regulators themselves?

[cj74]

No sweat. I've done more damage trying my own ideas. 😜 My plan is to place the 9V battery in the box so I would only need to connect one external power source. The switched 6 slow me to preserve battery life. They are 3 pole switches with the 3rd pole needed for the led. No regulation within the switch.

Just disconnected everything and wired up one circuit at a time. Everything working as expected. Only have issue when powering all circuits at once.

[RichD]

The voltage regulators that I have built can be turned up or down without a load. Here is what I am proposing, the original scheme is on the left. I left off the 9V stuff that powers the displays and the wires from the power supply for clarity.



I will try to look up the DSN-VC288s, I may have to make some changes.