New Test Box

[Steve L.]

Well, here’s Steve L.'s new "test" box.

It's designed to go between the tow and the trailer.

Most of the LEDs are self explanatory. The Trailer Charge LED lights if there is power going to the trailer battery. On the Ford, turn off the ignition key and the light goes out and the trailer is running off its own battery and not draining the tow vehicle's battery. I fabricated a 6 foot cable with two male ends for the tow to test box connection. It stores more easily if you can disconnect the cable.



The first picture shows it in Voltage setting. I tried to catch the turn signal LEDs when they were on (4 way flasher) but I couldn't time the shutter properly. They're red. Hard to see but the tow is putting out about 13.4 volts at idle.



The second picture shows it in Amperage mode with the reefer on 12v. I know the reefer is pulling about 10amp but this picture is showing only about 5 amps are being supplied by the tow while it's idling. The rest is being supplied by the trailer battery. I expect at the 1500 to 2000 rpm I cruise at this number would go up. One of these days I'll ask somebody to look at the meter while I hold the revs up some to see where I am.

At idle, all loads off, the tow is trickling about 1 amp to the trailer battery.

I remain convinced that the tow vehicle will not return a battery to full charge. Mostly based on my past studies with the Link 10. I will try it again when I'm dry camping. This is redundant to the Link 10 but I can take it to someone else's trailer to show them as well.

I have some LCD panel meters coming for me to play with. Version 2 will have two LCD meters permanently set on the face so that I don't have to carry the separate ammeter.

[Ed Harris]

We must be related!

[Gina D.]

Boxy... but nice!

(oops, sorry.. wrong auto maker )

[Steve L.]

Version 2.0 of Steve's Tow Test Box is ready! (Wretched excess, part 2.)

I know everyone's been waiting with bated breath (If you have baited breath, see your dentist or stop eating sushi. )

Version 2.0 includes built in volts and amp meters. For the tech weenies, technically the amp meter is reading millivolts across a 50A/50mv shunt. The panel meters were probably the least expensive part of this project at $7 and $9 respectively.




I switched on the reefer to get some sort of amp reading on the ammeter. Otherwise, practically nothing was going into the trailer from the tow.

Version 3.0 will combine the Trailer Test and Tow Test boxes into one box. But I'll need a bigger box. The Tow box is already stuffed with tidbits, (some heavy gauge wire, the backside of two meters, two 7 pin female trailer outlets, shunts, diodes, LEDs, switches, bus bar and terminal strip). The Trailer box has a circuit breaker, scads more switches and a 12vdc outlet. At least it'll share most of the wiring and 7 pin RV connectors.

I wonder how much current a circuit board will carry. How much current I'd like to try making my own circuit board. That would cut down drastically on the wires. I'll have to search around for that answer.

And to think I hated circuits class in college!

[Jim Meeks]

Steve L.
Watching for Version 3, good work. You will need 2 or 3 circuit boards for Versions 4 & 5. Good work.
Jim

[Ed Harris]

Steve

You are clearly insane.....ask me how I know?
Not that there is anything wrong with that.

http://forum.servomagazine.com/viewt...hp?f=1&t=14329

You can start here maybe and to be safe think even bigger.
I imagine it also depends upon the duty cycle you need but for just a short term reading it will be different than for sustained readings.

These are main reasons they use shunts to read current.

There are also several places that will make one-off boards and even have free layout software.

http://www.google.com/search?client=safari...-8&oe=UTF-8

They work fast and ship quality products in general.

Have fun
Ed

[peterh]

That would cut down drastically on the wires. I'll have to search around for that answer.

And to think I hated circuits class in college!

I, personally, don't like dealing with the acids and toxic waste from the process of acid-washing the copper off the PCB boards in the areas where you don't want a trace, so I use solderable perforated prototyping boards like these.

If you really want an etched circuit board, try looking for an acid-etch resist pen, which are felt-tip-pen type things that allow you to draw your traces on a copper-clad circuit board then run it through the acid wash and neutralizer. Any place that sells them will also sell the etching acid and neutralizer.

Hated circuits class? What, didn't like doing Kirchhoff's net current calculations? I can't imagine why . . .

[Dan Meyer]

This is really cool!

The only question I have is why not install it permanently into your trailer? Automotive panel gauges are cheap and readily available, and most of our trailers have a suitable space for this sort of thing.

-- Dan Meyer