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Outputs Switching Off
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 Posted: Tuesday May 6th, 2008 10:02 am
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cgiltrow
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Hi,

I have a Comfort I system with 2 slaves, both with LEMs.

I little while ago I installed a 12 zone irrigatrion system which I control with Comfort.  I use 12 outputs to drive relays which in turn switch 24vac to the sprinkler solanoids which in turn switch the sprinklers on and off.  I have programmed Comfort to go through a sequence of switching each of the irrigation zones on (via the outputs) in sequence (ie the first zone is switched on for 5 minutes then switched off then the second zone switched on etc.).  This has worked very well for a while.

The 24vac power supply was permanently on and this weekend I decided to implement some energy efficiency by connecting the power supply to the power outlet via a relay that I can drive from an output on Comfort.  Now I only switch the power supply on when the irrigation program starts and then I switch it off when the irrigation program ends.  The power supply is now not permanently on (and therefore more energy efficient). So When my program starts it first switches the power relay on, then the first irrigation zone for 5 minutes, then switched that zone off, then switches on the second irrigation zone, etc until the last irrigation zone is switched off after 5 minutes at which point the power relay output is also switched off.  The irrigation zone outputs are on the second slave (8) and the second slave LEM (4).

My problem is this:  When I switch off the first irrigation zone (after having switched the power relay output on and the first irrigation zone output on for five minutes) then the power relay output also gets switched off (I say "I" switch the outputs, but I mean I switch the outputs with commands in responses).  Comfort thinks that the output is still on (If I look at the output from WizComfort it says that it is on, if I query Comfort directly with "O?48" then the response I get is "O?4801" which tells me that the output is on), but actually the output is off (the relay is off and if I measure the current on the output it is 0v).  I moved the relay output around a bit and got the same result.  I did notice that this was the case when I had the power relay output on the outputs on the second slave LEM.  I then moved the output to an output not on the second slave nor on the second slave LEM (to output 32 - the LEM on the first slave). It seems to work better, but I still have other outputs on the second slave LEM that are getting switched off when one of the irrigation zone outputs are switched off (The irrigation zone outputs are on the second slave (8) and the second slave LEM (4).)(Sometimes when the first irrigation zone output gets switched off the other outputs are not switched off, but then one of the later irrigation zone outputs does switch the other outputs on the second slave LEM off when it gets switched off.  On one occation other outputs not on the second slave or second slave LEM also got switched off when one of the outputs on the second slave or second slave LEM got switched off.  In all these cases Comfort thought the output was still on, but the current on the output was 0v).

Please excuse my long winded expalination.

Your help will be much aapreciated.

Regards,

Clinton.



 Posted: Tuesday May 6th, 2008 12:37 pm
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admin
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Outputs on the LEM are sensitive to induced impulse voltages on the Flat Cable connecting it to the main controller or Slave. Ensure that the ribbon cable is far away from the relays as possible. Try to shorten the ribbon cable using the new Comfort II LEM cable if possible as the Comfort I LEM is mounted on the base of the enclosure and has a longer cable.

The voltage impulse comes from the back EMF of the relays when they switch off, see the article here which I googled on the internet http://www.jaycar.com.au/images_uploaded/relaydrv.pdf

You need a reverse diode across the coil of the relay as shown in the circuit. If you use Comfort Relays RLY01 or RLY02 these are built in, but no harm in adding an additional power diode

Move the sensitive relays off the LEM and into the main or SEM if possible

Comfort II LEM is mounted on the Main board and has a very short cable so it is less susceptiblle




 Posted: Wednesday May 7th, 2008 08:15 am
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cgiltrow
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Hi,

Thanks for the feedback.

Both the slaves are the newer slaves with the short ribbon cable and the LEM mounted on top of the slave.  The slaves are quite far from the relays (about 2 meters).  The slaves are housed in a shielded metal box.  The mainboard is Comfort I though.

Do you believe this can still be a feedback problem?

Thanks,

Clinton.



 Posted: Wednesday May 7th, 2008 12:34 pm
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I thought they were Comfort I Slaves
Can you give me the serial number and Firmware of these SEMs by private message



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