DC-AC-DC is it madness? Inverter insanity

**russ** · 02-21-2004, 03:31 PM

Hi All,

I think this is one area where searching just makes things less clearer

I don't have an opus or any DC-DC power supply but I do have a 150 watt inverter that I already have in my car. (And I may go the DC-DC in the near future but for now…)

I have already hardwired the power for the LCD (from off the cigarette wires )but when I measure the voltage at the pins and my car is running it gives a pretty constant 14-15V

My question is - whether it is safer to power your LCD off an inverter using the AC-DC 12V power plug which when measured gives a steady 12V at the pins. Forgetting about the inefficiency of this setup because my car is always running when I’m using the system.

I was wondering what the long term effects would be to run the LCD from the hardwired way giving the unregulated 12-15V - or is it a complete no no and stop right now!

I don't run my system with the engine off - and I use a laptop which has a 3 hour battery life minimum - so power for that is not a problem.

Can anybody help?

Thanks

Russ

**russ** · 02-22-2004, 03:12 PM

I guess what I'm trying to ask is whether it's safe to power the LCD off the accessory wire permanently with the unstable voltage?
Does the LCD manage it okay?

Russ

**hijinks21** · 02-22-2004, 03:25 PM

you safest bet is to power the lcd off the power supply

**russ** · 02-22-2004, 03:35 PM

thanks hijinks21,

So the inverter is safer then - good to know as I would have continued to power off the cigarette/accessory wire unless I had checked the voltage out.

But thanks again for your answer.

Russ

**kingo102** · 02-23-2004, 02:23 AM

Gday Russ,

Are you using the supplied cigarette power attachment that came with the lilliput (i'm assuming you do). It's the grey cable connected to the little egg looking thing. If so, you will have no probs with the 14+V apparent at the cigarette terminal. This is because in the eggy thing, there is a regulator circuit which ensures 12V is being output to the screen at all times.

As well as this, you should use this as opposed to the Inverter > Converter > screen solution for a couple of reasons. The inverter will undoubtedly introduce noise (as well as most probably being a triangular wave - which is merely a mimicked AC signal [bad news]). Also, as you introduce more steps of power conversion the system becomes more and more inefficent (power goes to waste through heat).

So def stick with the cigarette plug, or if you wish cut the plug of (ensuring that the regulator is still in the cable) and wire it in directly to the car battery or PSU (+fuses and swithes and relays - whatever bakes your cake). There is plenty about this in other posts.

Hope this helps,
Dave

**russ** · 02-23-2004, 08:24 AM

Hi Dave,

thanks for the reply.
My lilliput didn't come with a regulator - just a straight through basic cigarette power lead - which is giving a steady 15v out when the car is running!
When I pulled up a search on this before I posted this I could see people were running it off this egg shaped regulator power - I was thinking what the hell are those and why haven't I got one

would you recommend getting hold of one of these regulators for the lilliput?

Cheers

Russ