Design Advice

[Darrel Taylor]

The idea is to read the Current being sent to the reverse lights from the cab. It's actually an analog output from the current sensor, but with the sensitivity cranked up ... the output will be "High" (output saturated) with any current being drawn, and "Low" when there's no current.

Then in the trailer, it turns the lights on/off via serial data to the solid state relay.

For incandescent lights, fast on/off times won't be noticed visually. May cause a little dimming, but it only takes a few milliseconds to send the data so noone will even notice.

This way it doesn't matter what the voltage is on the line. Works on 12v just as well as 24V.

[ZOOM]

The idea is to read the Current being sent to the reverse lights from the cab. It's actually an analog output from the current sensor, but with the sensitivity cranked up ... the output will be "High" (output saturated) with any current being drawn, and "Low" when there's no current.

DT good explanation just like a squarewave

Then in the trailer, it turns the lights on/off via serial data to the solid state relay.

How are you going to feed this output back to the tralier as if i followed this tread correctly i think it was mentioned that the only connection between the trailer and the cab is going to be the 24V line ?

[Darrel Taylor]

How are you going to feed this output back to the tralier as if i followed this tread correctly i think it was mentioned that the only connection between the trailer and the cab is going to be the 24V line ?

There's no output from the cab to the trailer. Only the power being applied to turn on the Reverse(back-up) lights.

When the reverse lights are turned on, it powers a PIC in the trailer that's been pre-programmed with the trailers information in EEPROM (no iButton). That pic modulates the lights, which sends the data to the cab (via current) without the need for any additional wires.

The information would be sent only once or twice when the reverse lights are first turned on. Which is why I mentioned it could be done with the brake or turn signal too. Those will happen more frequently, and the Brake is guaranteed to happen when driving. Turn signals are not guaranteed, depends on the driver, but they're more likely than reverse lights.

[ZOOM]

When the reverse lights are turned on, it powers a PIC in the trailer that's been pre-programmed with the trailers information in EEPROM (no iButton). That pic modulates the lights, which sends the data to the cab (via current) without the need for any additional wires.

I see what you mean what a clever way to do this =)
But i still dont get it how the cab would be able to differentiate between two trailers
as with your earlier explaination

That pic modulates the lights, which sends the data to the cab (via current) without the need for any additional wires.

With the brake/Reserve pressed the input to the cab would be high all the time as the lamp is ON

[isaac]

I see what you mean what a clever way to do this =)
But i still dont get it how the cab would be able to differentiate between two trailers
as with your earlier explaination

Hi Zoom

It would work if i get what DT is saying is that if you can turn the normally ON solid state relay ON/OFF (with serial Data say 01010101 ) fast and quick enough for it not to be noticed by the naked eye,this data can then be read by the pic in the Cab from the hall effect current sensors analog output fed via say a Schmitt trigger you should be able to recover that 01010101 Data sent by the trailer
This way each trailer would have a different code differentiated by the Pic in the Cab

Hope i am right
Isaac

[Darrel Taylor]

Ding Ding Ding Ding!

Give that man a cigar!

Exactly!
<br>

[ZOOM]

Hmmm thats a very niceway of doing things
BTW what sensors are avaliable i want to make an experiment
must of the solid state relays i found are all N/C any links

Zoom