Driveway Beam Sensor Failing

[brucecampbell]

I'm getting frustrated with a beam sensor connected to a C4 contact which is working intermittently, hoping someone has some thoughts on debugging the issue.

I have had this beam sensor (LINK) for years and everything has worked well until recently.

Problems were occurring when it was connected to my HC300. the 300 has been removed and it is now connected to an HC800
The beam sensor is about 80m away from the controller and power supply.
I am using a 12V 5A power supply.
The sensor appears to be working and I read 12V at the sensor.
I have the contact from the sensor plugged into the controller via the 12V and SIG connection points
I read 12V on the contact when in alarm and 0V when not in alarm. - This tells me the relay in the sensor is working.
At this point the sensor icon on my iPhone C4 app shows in alarm too.
Perfect - all working as it should.

Then later on when I need it to turn my lights on as I walk down the path, nothing....

Always works when I test it, and fails later.

Anyone got any ideas before I go and buy a new beam sensor?

 

 

 

[WholeHomeControl]

Is the 12V 5A power supply just to power the beam sensor?  This is not wired into the HC800, correct?

When you trigger the sensor by walking down the driveway and your lights fail to turn on, what state does the sensor icon on your C4 app show?

Also, the link to the sensor times out for me. 

 

 

[WholeHomeControl]

> I read 12V on the contact when in alarm and 0V when not in alarm.

Where/how, exactly, are you taking this measurement?

Also, if you manually short the 12V and GND pins on the HC800, do the lights turn on?

[brucecampbell]

4 hours ago, WholeHomeControl said:

Is the 12V 5A power supply just to power the beam sensor?  This is not wired into the HC800, correct?

Yes, the 12V 5A power supplier is just to power the sensor, it is in no way connected to the HC800.

4 hours ago, WholeHomeControl said:

When you trigger the sensor by walking down the driveway and your lights fail to turn on, what state does the sensor icon on your C4 app show?

I can hear the beam sensor clicking - which I assume is the relay switching
At this time, the lights fail to turn on and the C4 app does NOT show in alarm

4 hours ago, WholeHomeControl said:

Also, the link to the sensor times out for me. 

Link supplied was NZ local online store - perhaps not available outside of NZ
It is this one found on ebay: Beam Sensor

 

4 hours ago, WholeHomeControl said:

Where/how, exactly, are you taking this measurement?

Using a multi meter on the physical contacts on the beam sensor.
reads just over 12V.
Wired using 6 wire security cable with a run of about 80mtrs. 

4 hours ago, WholeHomeControl said:

Also, if you manually short the 12V and GND pins on the HC800, do the lights turn on?

Good question - I will run this as a test.

Cheers.

[brucecampbell]

I’ve run another test tonight.
The contact on the beam sensor is reading 11.45V and shorting is not activating the lights.
Occasionally the voltage reached 11.7 and this was enough for the controller to respond.
Is there a way to boost the voltage?
Can I steal power from the supply to the beam sensor?
Or just add in another power supply?
How?
Any risks?


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[WholeHomeControl]

Hmm, I'd have thought 11.45V would be enough to trigger the contact sensor, but I don't know the actual specs.  Assuming the issue is in fact that the voltage drop is too large, you have a few options:

1. You mentioned that you were using 6 conductor security wire.  Have you trippled up the conductors (i.e. use 3 conductors for the 12V side and 3 conductors for the SIG side?)  If not, that's the first thing I'd try.

2. You can use an external power supply at the HC-800 that outputs more than 12V.  You wire this up as shown in the following diagram:

*** The key here is that you don't want to overdirve the contact sensor. I don't know the specs of the contact sensor off hand, but will try to track that down.  If you can, per chance, source an adjustable power supply, then just tune it so that you get 12V at the HC-800 after the current loops through the driveway sensor. ***

3. You can use an external relay that is more sensitive than the HC-800 contact sensor, and then wire NO and C from that relay to the 12V and SIG on the HC-800 contact sensor.

 

 

 

[brucecampbell]

Thanks for the help.

1. Yes I have 6 conductor, but 2 are used for the power supply, as this is located in the rack along with the controller. The other 4 are paired up and used for the sensor contact.
2. using an external power supply sounds like a good option for me to try.
Any reasons I can't just steal power directly from the sensor?

ie: 

[WholeHomeControl]

I checked the specs and apparently the hc800 sensor is supposed to trigger at just 3V. This makes me wonder if the problem truly is the voltage drop.  

Then again, it still may be that there isn’t enough juice from the hc800 12V pin to trigger the sensor over that distance. So, trying the beam power supply might make sense.

However, it sounds like the beam power supply is near the hc800, in which case I would connect the power through on the hc800 side, and not send the power through two round trips to the sensor.

I will post a diagram of this shortly  

 

[brucecampbell]

Thanks, I appreciate you help on this one.

I just remembered I changed the configuration a year or so back due to this kind of problem.
I previously used the NC connection, and all worked fine for years.
Then it would trigger seemingly randomly and my driveway lights were coming on all hours of the night.
I changed to use NO and all was working ok for a long time.
I've now tested the cable and one of the 6 wires has no reading - so is broken somewhere - bugger!
The other five read ok - but perhaps there is more damage causing some loss of voltage??

Anyway, I will push on with using the external power supply and see if that provides enough power to run this properly.
 

Would really appreciate the diagram when you have time.

Cheers.

 

[WholeHomeControl]

Ok, here’s the diagram. 
 

 

[brucecampbell]

Thanks. Up and running now.


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[WholeHomeControl]

That’s great. Thanks for the update.