Convert AO to DO

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cvdk

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May 16, 2019, 2:31:54 AM5/16/19
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I have 16 unused AO with my miniserver and my 3 extensions.
I would like to use it to have a few more digital outputs to send some 12V and 24V commands for electric curtains, alarm status, etc...

I saw on this forum that a good solution for that consist in using SPDT relays.

I found 2different models. The second one is cheaper (1$/output vs 5$/output) but i dont really see the difference.
Could you help me ? Wich one will you choose ?




 

cvdk

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May 16, 2019, 2:34:30 AM5/16/19
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Václav Novák

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May 17, 2019, 2:08:48 AM5/17/19
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Hi 

I had very similar idea but I didn´t buy it . I made the similar board myself. 
Still not working because no time to implement to my system.  Board is finished , soldered with parts. I had only 4 relay board in the case for DIN.
Output current from analog output   (input for relay) was solved. it is  used ULN2803. 

Actually I need 2 relays output but Extension are full. I am going to solve in very early.

Good luck
Vaclav 






Dne čtvrtek 16. května 2019 8:31:54 UTC+2 cvdk napsal(a):

Tico

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May 17, 2019, 2:51:49 AM5/17/19
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Be aware that the AO's have a maximum continuous output rating of 10mA. The first link (a) you provided appears to require driving the coils with a very small input control signal -

Input control signal high level current:
2.5V: 0.1mA.
5V: 0.35mA.
12V: 1.1mA.
20V: 1.9mA.

This should be fine for the AO's.

The second link (b) appears to be the same circuit-board design, but I can't see the input signal specs. I would hazard it would work fine also.

The third link (c) appears to have the coils driven directly. The 'Coil of resistance' specs don't make a whole lot of sense, so I'm using the Power Per Channel of 0.45W. That would suggest a coil current of about 90mA. That sounds about right for that type of relay. It's also well in excess of what the AO's could support.

cvdk

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May 17, 2019, 3:15:03 AM5/17/19
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Many thanks Tico. That's really more clear for me with your explanation.

It will use less space in my board and the signal input is 15mA.
It just doesnt work for alarm status signal output where i would like to use NO/NC to activate a green led (NO) and a red led (NC) with only one AO output from Miniserver.

Ian Norton

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May 17, 2019, 3:44:12 AM5/17/19
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I wrote a post about this a while back that might be helpful:


Regards, Ian.

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Tico

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May 17, 2019, 4:29:54 AM5/17/19
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It's quite a challenge to find relays that work with 10mA coil currents. The Loxone specs have the full details -


4 analogue outputs
  • 0 – 10VDC,
  • 12 bit resolution
  • Maximum momentary output current: 20mA
  • Maximum continuous current: 10mA

I've been using these relays successfully for a couple of years -


They will do your NO/NC circuit for LED's on one AO. They draw 13mA at 10V (actual measurement).

Check the Technical Datasheet at the link. Go to the last page and the schematic I'm using is the '1 Form A 1 Form B type', Single side stable.

DK Relay.png

Duncan

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May 17, 2019, 5:30:44 AM5/17/19
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these work fine and are zero crossover so are great for switching mains leds, but are taller than uk din rail parts and require the front opening to be made bigger to fit in ( or a deeper set rail so the top wont need to poke out at all

duncan

cvdk

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May 17, 2019, 9:07:35 AM5/17/19
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OK. If I understand everything the slim one in my last post is not ok because i will need a continuous output of 15mA to close the relay. This will ok tmporary but not continuously. Is that correct ?

Tico

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May 17, 2019, 7:31:04 PM5/17/19
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I think Duncan suggested the slim one is fine at 15mA. We are talking some minuscule differences in current...I think the slim ones should work fine also.

The AO's were originally specified with an output rating of simply 20mA. At some stage, Loxone changed this to 10mA continuous, 20mA momentary. Whether that was due to some pattern of failures, and Loxone were being particularly conservative, I can only speculate.

I can't provide authoritative guidance other than to observe that 13mA has been working with mine for a long while.

Duncan

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May 18, 2019, 3:58:30 PM5/18/19
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David Wallis

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May 21, 2019, 8:54:08 AM5/21/19
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with regards to the current - it might be due to the sum of all outputs or current limitations within the voltage reg on board causing voltage fluctuations and crashes. _ just guessing here:

according to info here the AO's are driven by an AD5724  info here https://www.analog.com/media/en/technical-documentation/data-sheets/AD5724_5734_5754.pdf over current can be enabled by " The configuration of the overcurrent protection is selected via the clamp enable bit in the control register" which your not going to be able to see.. 

Eitherway the IC supports 20ma so I would be tempted to give it a whirl, just make sure you have flyback diodes on the relay coils and think about whether every relay would be on at once.. If so then drive via an opto isolated relay board, plenty availble for arduino's etc that could be made to work.

Brad

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Jul 26, 2019, 10:03:37 PM7/26/19
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Are the AO capable of doing +/- 10v? I found some latching relays that I might be able to use all my open analog outputs for, but it looks like it's a 2AO for 1DO solution. I want latching relays so I don't have to keep a current applied to the cool to hold the contacts closed. I am wanting to wire my outlets up to some relays so I can do load shedding if I lose utility power.

Am I missing something?

https://au.element14.com/schrack-te-connectivity/rt314f12/relay-spdt-250vac-16a/dp/1175083

David Wallis

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Jul 27, 2019, 5:20:03 AM7/27/19
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I think you are over complicating it with trying to use latching relays - think of the logic you will need just to turn something off or on. IE just use a normal relay. If your concerned about the current - get some of those relay boards with opto isolators and then the only current is driving the opto isolator.

Duncan

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Jul 27, 2019, 4:01:33 PM7/27/19
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Or just use a solid state relay

cvdk

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Jul 21, 2020, 7:00:54 PM7/21/20
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Hello. I finalise this project.

What do you think about that to convert the AO to DO ?

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