Hiya can someone help?. I have been trying to add a microphone to my CCTV system the problem is when I use one of those 240 vac to 12 vdc adapter's I get sound from the microphone but a hell of a lot of interference I know it is originating from the adapter but don't know of a alterative way of powering the microphone . Any help would be greatly appreciated thanks Keith .

 

Your adaptor is probably switch mode and they do generate lots of interference.
You could use a linear one instead.
For instance:
Unregulated so voltage will probably be a couple of volts above 12V: http://www.ebay.co.uk/itm/Replaceme...231023?hash=item48a19f83af:g:eh0AAOSwYHxWL2OK

 

Use a plug in microphone like these, i use them outside as well...clear sound no noise.


https://www.google.co.uk/search?q=c...&ved=0ahUKEwiRyvjxscDWAhXDalAKHeJQC8MQgjYInwY

 

Your adaptor is probably switch mode and they do generate lots of interference.
You could use a linear one instead.
For instance:
Unregulated so voltage will probably be a couple of volts above 12V: http://www.ebay.co.uk/itm/Replaceme...231023?hash=item48a19f83af:g:eh0AAOSwYHxWL2OK

Thank's I've ordered one of eBay with your link .I have tried several adapter's but not a linear one so I was just going round in circles so thank's again Keith.

 

Use a plug in microphone like these, i use them outside as well...clear sound no noise.


https://www.google.co.uk/search?q=c...&ved=0ahUKEwiRyvjxscDWAhXDalAKHeJQC8MQgjYInwY

Thanks but I have several microphone's so I just needed a power source . I have ordered a linear adapter so hope that work's thank's for your help Keith .

 

Is it not possible to pick up 12 volts from the CCTV system to power the microphone. It will only require a few mA. I would also suggest putting say a 1K resistor in series with the positive and an electrolytic capacitor of between 10 an 100 uF between 0 volts and the microphone side of the 1 K resistor. This may even work with one of your switch mode power supplies. It may also be worth putting a 100nf mylar or ceramic capacitor in parallel with the larger capacitor as it will filter out high frequencies better than an electrolytic capacitor.

Les.

 

Is it not possible to pick up 12 volts from the CCTV system to power the microphone. It will only require a few mA. I would also suggest putting say a 1K resistor in series with the positive and an electrolytic capacitor of between 10 an 100 uF between 0 volts and the microphone side of the 1 K resistor. This may even work with one of your switch mode power supplies. It may also be worth putting a 100nf mylar or ceramic capacitor in parallel with the larger capacitor as it will filter out high frequencies better than an electrolytic capacitor.

Les.

Thanks for your help . I am going to try the linear adapter idea first as it is simpler ( save's me getting the ladder out again ) Keith