Integrating digital systems to 0v relays

Thread Starter

Charlieecc

Joined Dec 16, 2022
3
Hello all and thanks for visiting the thread. I work with the automation of systems using radar and need some help due to the degradation of ducting in the UK.

We would usually send our 0V open or closed messages over cable to the receiving unit straight from the outputs on my radar product, however, I am looking in to the possibility of sending the open or closed circuit messages over WIFI or Bluetooth (anything with low latency and low power consumption). Is there a stand alone product out there that will simply convert a open or closed circuit to a digital message and back to a physical at the receiver end?

Sorry for being vague and if I need to put further info please ask.

Cheers in advance

Charlie
 

Ya’akov

Joined Jan 27, 2019
9,248
Welcome to AAC.

The short answer is “yes”, what you are looking for exists in some form. The longer answer involves knowing more.

What is the distance between the devices?
What is the maximum permissible latency?
What is the required reliability?
What is the maximum permissible power consumption?
What is the current signaling method (e.g.: dry contact, TTL out, etc.)? (I am guessing that by 0V you mean dry contacts but I am not going to assume).
 

Thread Starter

Charlieecc

Joined Dec 16, 2022
3
Welcome to AAC.

The short answer is “yes”, what you are looking for exists in some form. The longer answer involves knowing more.

What is the distance between the devices?
What is the maximum permissible latency?
What is the required reliability?
What is the maximum permissible power consumption?
What is the current signaling method (e.g.: dry contact, TTL out, etc.)? (I am guessing that by 0V you mean dry contacts but I am not going to assume).
Thanks for the reply,

Distance less than or equal to 75m
Latency would need to be sub 1 second but ideally sub 5ms
Reliability ideally above 95 percent
Power consumption is not a huge factor at the moment however the lower the better, operating from PSU of upto 48v although 12v and ELV also are available.
Current method is dry contact

Again I understand I am being rather vague but the nature of the use cases makes it difficult to give too much info.

Thanks
 

Ya’akov

Joined Jan 27, 2019
9,248
Thanks for the reply,

Distance less than or equal to 75m
Latency would need to be sub 1 second but ideally sub 5ms
Reliability ideally above 95 percent
Power consumption is not a huge factor at the moment however the lower the better, operating from PSU of upto 48v although 12v and ELV also are available.
Current method is dry contact

Again I understand I am being rather vague but the nature of the use cases makes it difficult to give too much info.

Thanks
Sorry, I missed your response.

How much space can this occupy?
Can it be outboard (tied to the existing dry contact?)
Is it a retrofit or part of a new design?
What is the budget?
 

Thread Starter

Charlieecc

Joined Dec 16, 2022
3
Sorry, I missed your response.

How much space can this occupy?
Can it be outboard (tied to the existing dry contact?)
Is it a retrofit or part of a new design?
What is the budget?
It would hopefully fit inside our IP enclosure which is around 30cm x 15cm x 10cm
Yes can be tied to existing contact
Both new and retro fit ideally
Budget at the moment is speculative so ideas welcome
 

Ya’akov

Joined Jan 27, 2019
9,248
It would hopefully fit inside our IP enclosure which is around 30cm x 15cm x 10cm
Yes can be tied to existing contact
Both new and retro fit ideally
Budget at the moment is speculative so ideas welcome
There are commercial products that are not inexpensive. They tend to be based on Zigbee, which is a very solid set of protocols and even based on an IEEE standard (IEEE 802.15.4).

Most of these products attempt to simulate a wire between a dry contact and a relay. But, as I said, not cheap. NCD is typical of the category. The products in this class will be reliable, but they will also be on the large side and, to repeat, cost a lot.

If I was going to do something like what you are talking about with the level of experience you have and the fact that this is a secondary thing to your main product, I would take one of two routes:

Hire a design engineer to integrate some general purpose wireless module—it could be zigbee, or WiFi, or something else, into your product with the view to using it for this and any future wireless needs.

WiFi is an attractive option for a variety of reasons but, though security should always be one of the very first considerations when you are doing wireless control of anything (and telemetry that will be acted on is the same as control), in the case of WiFi it is particularly important because of the extended capabilities and standard nature of it.

That said, it’s not rocket science to secure it, it just has to be attended to. If you had a small WiFi capable MCU as part of your device(s), it would open an array of future possibilities that would require only firmware to implement including remote monitoring and reporting, remote control, and time synchronization.

I would strongly suggest using MQTT for the communications.

The second route would be the same, except to do it yourself. This is both not as hard as it sounds and probably not as easy as you‘d like. A small, cheap WiFi enabled MCU like the ESP8266-based ESP-01 can easily be made to use MQTT and as a consequence easily and reliably operate something like a Shelly IoT wireless relay¹ which looks cheap and cheerful compared to the NCD options and natively supports MQTT.

The Shelly modules are ready-to-go and can be run from Mains or low voltage DC.

So, basically, I think it is far more sensible to invest in creating a general purpose wireless capability than the narrow use case because there will be little if any additional effort to do it that way, and because it will add a lot of value to your product. I don’t know if any of this is attractive but if you have questions, just ask.

1. I don’t know where you are located but don’t worry if the Euro prices made you cringe, Shelly is available worldwide, and even on Amazon.
 
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