Voltage - how or low; is it a real issue?

[JohnI.Stephen]

I recently purchased a pair of video transmitters so enable me to transmit a video signal (rear view CCTV) from the caravan to the tow car. The transmitters are 8v and come with 240v to 8v adapters; however these adpaters can't operate in the car and caravan when you're towing ! I therefore bought a pair of 12v -->12v and less DC cigarette lighter adapters. However they go from 12v to 9 to 7.5 and down. I have been using 7.5 volts but they are temperamental. Do you think that to run them from 9 volts would damage or blow them; seeing as this is but 1 volt higher than the stated correct 8v input...?

Thanks

John

 

[rob_jax]

Hi John,

There are no common electronic devices that need 8V, usually 5V or 3.3V - and the CCTV will have it's own internal regulator for precision voltage control.

If the 240 Volt to 8V PSU is unregulated, then you may see 12V or more if you put a digital voltmeter across the output - this is common for an unregulated supply driving no load - and will drop back to 8V when loaded.

Likewise the car adapter, but they will probably be quite close to the target values. Measure the no load voltage on both 7.5V and 9V. If the car adapters don't have the ability to supply the necessary current, then the voltage will be drawn down.

Having done all that, if the car adapter 9V no load is lower than the mains adapter 8V no load, then give it a go. You will be unlikely to blow any components, but the extra 1V may make the internal regulators run a bit hotter - as they may have some extra voltage to dump.

Robert

 

[JohnI.Stephen]

Hi John,

There are no common electronic devices that need 8V, usually 5V or 3.3V - and the CCTV will have it's own internal regulator for precision voltage control.

If the 240 Volt to 8V PSU is unregulated, then you may see 12V or more if you put a digital voltmeter across the output - this is common for an unregulated supply driving no load - and will drop back to 8V when loaded.

Likewise the car adapter, but they will probably be quite close to the target values. Measure the no load voltage on both 7.5V and 9V. If the car adapters don't have the ability to supply the necessary current, then the voltage will be drawn down.

Having done all that, if the car adapter 9V no load is lower than the mains adapter 8V no load, then give it a go. You will be unlikely to blow any components, but the extra 1V may make the internal regulators run a bit hotter - as they may have some extra voltage to dump.

Robert

Thanks Robert; A comprehensive reply but it does mean that I need to buy a volt / amp meter; for lost of things; this and the solar panel !! cheers

John