External power for 3xTemp/Humidity

[pest]

Hi

I'm setting up my first basic 1-wire net, currently involving a USB adapter and 3 Temp/Humidity devices.

My test setup worked fine with the 3 devices connected close together, ie. a 2M cable from the USB adapter to the first device, then 0.5M patch cables between devices.

Now I've placed them through the house though, I'm having issues seeing the devices at all. I can get some of the temperature sensors, but none of the humidity sensors. My guess is that the extra distance (~30M to the furthest device) means not enough power in parasitic mode.

I've ordered a hub, partly to act as a power injector, but it'll take a couple of weeks to arrive and I'm impatient

My question is, can I temporarily hook up a 12V battery or 15V DC power supply (I have a multi-voltage jobbie lying around) directly to pins 7 and 8 and power them that way until the hub arrives? Am I likely to blow anything up using this approach?

Thanks.

Luke in NZ.

 

[ericvic]

That should not cause any problems, Just make sure not to cross positive with ground.

Eric

 

[pest]

That should not cause any problems, Just make sure not to cross positive with ground.

Eric

Well I've hooked it up and while on the positive side nothing blew up and no magic smoke came out, on the negative side it didn't help

The power supply I've used is a multi-voltage unit currently set to 13.8V. It can do 5V as well, would I be better to hook it up to the 5V pair instead?

When I plug the 1st device in, it reports fine, but when I plug in the other 2 devices (on the end of a much longer wire) all devices disappear. Occasionally one of the devices, like a thermostat, will appear briefly. Am I right in thinking this is a wire length issue? I thought 1-wire should be good to ~50M?

Luke.

 

[ericvic]

Most of our devices don't use the +5v so that wouldn't help.

The length shouldn't be a problem as long as you are using CAT5 and do not have it wired in a star topology.

Eric

 

[apostolakisl]

I hooked a one wire device up to 8volts once and it fried it. It started reading about 100 degrees hotter than correct even after powering properly.

 

[pest]

Still having no luck, this is making me a very sad panda

I can't add in more than a couple of meters of cable before devices start dissapearing. I moved the USB device to my Windows 7 machine to see if somehow Linux was the cause, but the symptoms are the same.

I thought perhaps the flat phone wire I was using between the USB adapter and the first device (about 1.5M long) might be causing issues, so I've crimped an RJ11 onto some cat5 but still no good.

Just a test on my desk with some patch leads of USB adapter <-- 2M --> 1st device <-- 0.5m --> 2nd device <-- 5M --> 3rd device fails. Only the first and secons thermostats reliably appear, none of the humidity sensors appear. If I unhook the 5M cable, the 1st and 2nd devices show up fine.

This has really got me stumped.

BTW, What does JP1 on these boards do? The first one I bought had it open, the 2 new ones have it closed. What should it be?

Luke.

 

[JimTolbert]

Try replacing the plugs on the 5m cable. I found that "ALL" of the commercial cables I had caused some sort of device drop out.

 

[ericvic]

Luke,

The jumper enables/disables the onboard voltage regulator. If you are not providing external power then you need to remove the jumper.

Eric

 

[pest]

Luke,

The jumper enables/disables the onboard voltage regulator. If you are not providing external power then you need to remove the jumper.

Eric

Yay! Thanks Eric, removing those from the newly acquired units fixed it. No bodged up external power required

I searched the site to find out what that jumper was for, unless I'm blind (it's happened before) you might want to add that tidbit to your how-to's.

Cant wait for the rest of the kit to arrive now!!

Luke.

P.S. I don't suppose anyone here has ever tried to turn an MSP430 into a 1-wire slave? That's my next project

 

[ericvic]

Luke,

Glad you got it working. I thought the info about the jumper was in the How-To section but I could be mis-remembering things.

Eric