ibuttons

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Texy

Senior Member
Indeed they are useful - the company I work for base their product licencing on them. Not much use for the hobbyist though.

Texy
 
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MFB

Senior Member
Yes, there are lots of "standards" but I was thinking more along the lines of a single wire version, like LIN.
 
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Dippy

Moderator
Why not draw up a plan of attack? Maybe have a go?
But I wonder whether one-wire across a vehicle is as easy as you think. If I had loads of spare time I reckon I'd have a go just out of interest.

One area I'd like to see someone do work on is the caravan/trailer electrics. That clunky old multi pin plug (sometimes 2) could be replaced by a 2 or 3 pin connection. Maybe done before. Get that into the Motor Industry via Dragon's Den and you'd be laughing ;)

Re: that Maxim device. If you are going mini s/m then fine, but why bother with it for pth? The s/m format just saves space. The operation isn't magic. For prototyping it'll only save a fingernail size bit of pcb space. For production go for it.
 
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westaust55

Moderator
Dippy said:
One area I'd like to see someone do work on is the caravan/trailer electrics. That clunky old multi pin plug (sometimes 2) could be replaced by a 2 or 3 pin connection. Maybe done before. Get that into the Motor Industry via Dragon's Den and you'd be laughing ;)
Click to expand...
Not sure that it will be possible to ever do away entirely with the old multipin plug and socket on caravans.

At least here in Australia where people often travel long fdistances in warmer weather, they want to keep the fridge running on 12Vdc while travelling. These fridges often draw 15Amps or more. In fact some/many add a second 60Amp plug and socket specifically for this.

Still also have to get adequate power on a separate line for the electric brakes.

It may come down to a CAN bus or similar to activate the turn, brake and clearance lights - but even these still need a main wirte as the source of power irrespective of on-board switching/control.

There would still need to be at least 3 heavy duty connections for Fridge, brakes and earth return (legally not allowable to using the tow hitch as an earth return). To avoid draining a battery when parked for extended periods, fridges here are often on a separate circuit with some form of cutout for when the tow vehicle is stationary.
 
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MFB

Senior Member
It certainly would be interesting to know how an iButton network operates in an automotive environment. The iButton interface and network protocol does not seem that different from many established one-wire automotive standards (SAE J1850 and LIN etc). Although microcontrollers and adaptors are available that connect sensors to such networks, iButtons would provide sensors, conditioning and interface in a single robust case.

I might try measuring a few temperatures around my car and see how it goes. Has anybody else tried iButtons for this application?
 
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Dippy

Moderator
I must admit I didn't know electric brakes were used. OK, 4 pins :)
Some cars have electric hand/parking brakes operated electronically, so if they can do it so can we. I'm kidding.
 
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Michael 2727

Senior Member
As far as I know most iButtons are simply the "chip" equiv jammed into a can.
e.g. the DS1920 Temperature iButton is a DS18B20 in a can.
the DS1990A ID iButton is a DS2401 chip in a can.
the DS1921 Thermochron Logger iButton is a DS18B20, DS1307 and DS1996 in a can.
(don't quote me on the exact chip #, examples only)

The ID Buttons only need a brief "clack" across the terminals to transfer their ID code
but the Temperature buttons (DS18B20) may still need the 0.7 sec to perform a correct
data transfer as the DS18B20 spec sheet.

Unfortunately my serial port iButton holder won't reach out to the car :)
 
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