I would like to know how to make a circuit that will close a dry contact (small relay) for maybe around 200ms to 500ms or so, on hearing a loud noise (with sensitivity control). Preferably with a small lead mic, that can be positioned to suit, away from the PCB.

There are many sound activated kits available, but basically I need one that is just for a “dry pulse” trigger, with a low latency, which will then be used for a PLC input. Most are latching, or have long "on" periods. I will have a 24v (not sure either AC or DC supply) for the plc, so if the circuit could be powered by the same, it would make things easier.

I’m not an electronic buff, but can solder/construct, if I know which components to use. I would be so grateful for any help on this, as I have tried for ages elsewhere to find this info, to no avail.

Thank you so much.

 

What is a "dry contact" or a "dry pulse"?

 

What is a "dry contact" or a "dry pulse"?

By this I mean a normally open contact (like a relay contact) that closes when the circuit is activated. Dry, means it has no actual output (voltage), but just acts as a switch. By pulse, I mean it isn't latched. It basically stays on (active) for a brief period, ie "pulse". Like a momentary switched relay.
Thanks

 

This circuit, with some modifications, would do the job:
http://www.electroschematics.com/704/sound-activated-switch/

 

This circuit, with some modifications, would do the job:
http://www.electroschematics.com/704/sound-activated-switch/

Hi, yes I have seen this and others, however, I wouldnt have a clue as to what are the modifications. I'm not knowledgeable about electronic circuit design unfortunately, hence my request here on this forum.

Thanks.

 

Can you check what supply voltage you have available and whether it is AC or DC, please?
That is the biggest change required to make this work for you.

 

Can you check what supply voltage you have available and whether it is AC or DC, please?
That is the biggest change required to make this work for you.

Hi, I'm not sure yet, but, I am going to be using PLC's and pneumatic rams (with solenoids), and I have been informed that the industry standard is usually 24v, as there is more readily available equipment in 24v. However, I'm not sure if this will be AC or DC, as I forgot to ask (doh!). I would say however that if we consider it to be 24v AC, as adding a simple rectifier if require, isn't much of a task.
I do have some basic underpinning electrical knowledge, as I am a qualified electrician, however, electronics I have never really delved into.
I have just found a simple circuit on you tube which might be what I'm looking for ie

which I guess would only need a simple voltage reg of some sort from 24V down to 9v. I would be interested if anyone has a comment on the you tube video. Thanks again guys.

 

24V AC gives about 33V when rectified so it really matters whether the 24V is AC or DC.

 

Hi, I'm not sure yet, but, I am going to be using PLC's and pneumatic rams (with solenoids), and I have been informed that the industry standard is usually 24v, as there is more readily available equipment in 24v. However, I'm not sure if this will be AC or DC, as I forgot to ask (doh!). I would say however that if we consider it to be 24v AC, as adding a simple rectifier if require, isn't much of a task.
I do have some basic underpinning electrical knowledge, as I am a qualified electrician, however, electronics I have never really delved into.
I have just found a simple circuit on you tube which might be what I'm looking for ie

which I guess would only need a simple voltage reg of some sort from 24V down to 9v. I would be interested if anyone has a comment on the you tube video. Thanks again guys.

I meant to add, I could just maybe add a small relay in place of the LED (or in parallel) to give me the dry contact could I not?

 

24V AC gives about 33V when rectified so it really matters whether the 24V is AC or DC.

Oh... I will have to find out for sure.

 

24V AC gives about 33V when rectified so it really matters whether the 24V is AC or DC.

I'm going with 24vDC. It seems that that is industry standard.

 

Here is a modified circuit which will work with a 24V supply and most common electret microphones.