Help on tapping 300V DC out from 12-220V power Inverter

[ma_sha1]

To build a 260W UHP short arc spotlight, I need to feed the ballast 300-350V DC.

I am trying to to tap the High DC out from my 12V DC-220V AC power inverter.
rated 350W.

Here is a shot of the Power Inverter opened up & you can see the Capacitor with
450V written on it.

Where do I solder to get the 300-350 DC out of it? Is it possible to tap it from the top side or do I need to take the whole thing out & try to find the 12V DC from the under side?

Some kind of drawing would be greatly appreciated! I am a noob about circuits.

Thanks for helping!

[45/70]

The "450V" on the cap is a rating not a voltage that is present in the cap. It just means that the cap is rated at up to 450 Volts. There is no voltage higher than 220 Volt in your power supply.

Edit to add that for your PS to even have 220 Volts, the mains suppling it have to be 220 Volts. If your PS is hooked up to 110 Volts, then that is the highest voltage that is available.

Dave

[45/70]

Eh, on second, thought your refering to an inverter, not a power supply. In that case the highest voltage available is ~ 220 Volts.

Dave

[ma_sha1]

Thanks, but this has been done before.
http://www.candlepowerforums.com/vb/...o-120-Watt-UHP

Unfortunately, he didn't post details on how he tapped 300V DC out of the inverter.
For my Power Inverter,
The input is 12V DC.
The output is 220AC, 350W.

There is another guy who did this but his posts were lost. & he told me just find the Capacitor & tap the DC. maybe not 450V but it's 300V-350V or so.

The invertor works by first make 300V or so DC from the 12V input, then chop it up & down convert to 220V AC,

so, yes, there is higher than 220V in DC form on this board somewhere, just need to fin it

[Mr Happy]

If you are a "noob about circuits" it is highly recommended that you don't try to mess with high voltage, high power circuits as a learning exercise. You could kill yourself. Really, no kidding.

Please, put the lid back on and leave it alone.

[BoarHunter]

Please don't try to destroy the short but eventfull career of a potential Darwin's Award candidate !

[ma_sha1]

Thanks Guys

I am not good at circuit but I am pretty good with electricity, don't worry.
Plus, the power source is from a portable battery pack, about half of the energy of a Car battery,
not from the wall outlet. the volt is high but not as much punch behind it as the wall outlet.

I am extremely careful, but I need to do this.

So, still need some help from experts on where to tap for 300V DC

[Mr Happy]

The danger is from that 450 V capacitor you are looking at. When charged, that contains easily enough energy to kill you.

If you knew enough to safely attempt what you are doing, you would not need to be asking here. You would know how to safely discharge capacitors with a suitable resistor, how to follow a circuit and how to trace voltages with a meter.

Given your current level of knowledge, you really should not attempt this.

Bear in mind that an electric shock with as little as 50 joules could kill you, and a single AA cell contains about 10000 joules. That is 20x more energy than is needed to end your life. Your comments about what might be dangerous are very naive.

[billcushman]

Please follow the recommendations you have been given about safety. High voltages can easily deliver "The fatal current" as Tektronix used to describe it. The fatal current is relatively low. It stops the heart and you are dead. Higher currents burn you and knock you away. If you don't already know these things, you should not be attempting your project. Please be safe.

[Russel]

[...]Plus, the power source is from a portable battery pack, about half of the energy of a Car battery,
not from the wall outlet.[...]

A common 9V battery is enough to kill. Half the energy of a car battery is far more than enough! I agree with Mr Happ and Billcushman, you shouldn't attempt tapping power from inside of an inverter!

[mvyrmnd]

Rather than modify an existing device, you could get a transformer to step 220v AC up to 700v then use a bridge rectifier to bring that back to 350v DC.

If you were crazy enough, you could build it yourself, but as it has already been said, it would probably result in natural selection.

Find an electronics guru to build you a custom power supply.

[MikeAusC]

Thanks Guys

I am not good at circuit but I am pretty good with electricity, don't worry.
Plus, the power source is from a portable battery pack, about half of the energy of a Car battery,
not from the wall outlet. the volt is high but not as much punch behind it as the wall outlet.

This is attitude will kill someone very quickly - 300 volts DC will kill much faster than 110 volts AC.

[MikeAusC]

Eh, on second, thought your refering to an inverter, not a power supply. In that case the highest voltage available is ~ 220 Volts.

Dave

No, 220 volts AC means a peak voltage of over 300 volts, so the capacitor will have well over 220 volts on it.

[HKJ]

Here is a shot of the Power Inverter opened up & you can see the Capacitor with
450V written on it.

That capacitor is probably the place to find the high DC voltage. It looks like for diodes that is standing next to it, you might also be able to find the voltage there. Try following the traces from the capacitor to the diodes.

If you short anything, you will probably blow the inverter and touching the wrong places will give you a very nasty jolt! (It might also kill you, especially if the current run through you heart and you have a weak heart).

[saeckereier]

The 9V story was interesting.

If you get shocked you should know that you should call an ambulance and get to a hospital to be monitored. Electrical shocks can cause small arrythmias that can lead to cardiac arrest up to 48h after the incident so proper monitoring is critical in that period.

[ma_sha1]

Thanks for all the concerns, guys. The 9V story is interesting, didn't know breaking the skin
make such a big difference, so going forward, we should never play with electricity with a cut & band-aid on.

With the skin on, electricity travels along the skin, so 110 shock rarely kill people unless one touch the wire with palm & close on the wire due to muscle contraction.

Some electricians in Asia countries test 220V AC wires with bare hand some times, the rule is always test with back of the hand, the shock will bounce the hand away. Never touch with palm, as muscle contraction will cause grabbing the wire & won't let go

I am sure most of you have felt the jolt from 110V AC some time during your life?
DC Volt risk is rated roughly as 1/3 of AC risk, so 330V DC is about 110V AC in risk, which is lower risk than 220V AC. But still, I am not under estimating the risk, I'll be extremely careful.

[Mr Happy]

DC Volt risk is rated roughly as 1/3 of AC risk, so 330V DC is about 110V AC in risk

Where are you getting this nonsense from?

As has been pointed out any voltage high enough to disturb your heart rhythm is dangerous, potentially lethal. That includes 110 V AC.

Yes, many of us have been jolted by the mains, even 240 V, in our lives. That does not mean 240 V is safe, it just means we have been lucky.

[ma_sha1]

I never said it's safe. It's relative risk info. I found by reading, but regardless, we are getting off topics here.

OK, moving right along, I found the Hi DC Volts I was looking for

I connected My volt meter black probe to the negative of the 12C in. Connected DC to 12V supply.Wear gloves in both hands & only held the red meter probe to look for the volts alone side of the capacitor


This pic. shows blow-up view of the 4 rectifier diodes, the leads coming off the top measured positive DV volts.The two on the side, measured 145 DC volts. The two in the middle, which appears to be connected on the board together, measured the same 290 DC Volts.

Now, I think I'll solder a wire to the two legs in the middle together (Increase current handling on the diode legs by 2x) to tap the 290V +.




My Only question remaining:

Should I be OK to use the 12V Neg Input as the "-" for my planned 290V DC outlet?
Or do I have to gain access to the "-" underside of the two middle diodes to use as "-"?

Obviously, the 12V input is much easier to access & by pass lots of circuit trace which increase current handling & reliability.

Thanks

[HKJ]

My Only question remaining:

Should I be OK to use the 12V Neg Input as the "-" for my planned 290V DC outlet?
Or do I have to gain access to the "-" underside of the two middle diodes to use as "-"?

Obviously, the 12V input is much easier to access & by pass lots of circuit trace which increase current handling & reliability.

Thanks

I do not know the schematic of the inverter, but I would suggest that you search some more for the minus. Just because the meter shows some voltage does not mean there is a direct connection. It is probably present on the downside of the two other diodes (D3, D7).

[45/70]

No, 220 volts AC means a peak voltage of over 300 volts, so the capacitor will have well over 220 volts on it.

I hadn't taken that into consideration. I always think in RMS voltage for some reason, when it comes to AC I guess.

If you knew enough to safely attempt what you are doing, you would not need to be asking here.

This is also why I probably shouldn't have posted in this thread!

Carry on ma_sha1. Do be careful though.

Dave

[VegasF6]

Thanks for all the concerns, guys. The 9V story is interesting, didn't know breaking the skin
make such a big difference, so going forward, we should never play with electricity with a cut & band-aid on.

With the skin on, electricity travels along the skin, so 110 shock rarely kill people unless one touch the wire with palm & close on the wire due to muscle contraction.

Some electricians in Asia countries test 220V AC wires with bare hand some times, the rule is always test with back of the hand, the shock will bounce the hand away. Never touch with palm, as muscle contraction will cause grabbing the wire & won't let go

I am sure most of you have felt the jolt from 110V AC some time during your life?
DC Volt risk is rated roughly as 1/3 of AC risk, so 330V DC is about 110V AC in risk, which is lower risk than 220V AC. But still, I am not under estimating the risk, I'll be extremely careful.

That's doing it old school yo! Hah. Don't forget to always keep the other hand in your pocket or behind your back. At least, that's what the old timers have told me. Somehow, they were still alive to tell me this. You know, the guys that can't be bothered to shut off 480V while they hookup a circuit cuz it would slow production.

Oh P.S. I am not so sure those latex gloves are affording you anything other than a false sense of safety. I am not gonna harp on it or anything, just want to point it out.

[italianboy]

You could just access the other side of the board and solder the two wires for high voltage DC in parallel to the two leads of the 450V-rated capacitor. Be sure not to short them to the outer aluminum shell!

[ma_sha1]

The back is not easily accessible as 5 resistors are thermo glued to the frame.

I measure the resistance between the - of the rectifier and - of the 12v in, it's Zero.
So I think it's the same to use either one.

[MikeAusC]

If you get shocked you should know that you should call an ambulance and get to a hospital to be monitored. Electrical shocks can cause small arrythmias that can lead to cardiac arrest up to 48h after the incident so proper monitoring is critical in that period.

Unfortunately I can verify the seriousness of that recommendation - sadly a colleague of mine died that way many years ago.

[MikeAusC]

. . . . Some electricians in Asia countries test 220V AC wires with bare hand some times . . .

Some people play Russian Roulette and live . . . . but there's no way I would suggest people doing that either !!!

[saeckereier]

Unfortunately I can verify the seriousness of that recommendation - sadly a colleague of mine died that way many years ago.

Sorry to ask, but is this something you witnessed first hand? (not the shock but the consequences) I have heard some reports of this and I have been taught this in training but so far I only heard third hand accounts.

[MikeAusC]

Sorry to ask, but is this something you witnessed first hand? (not the shock but the consequences) I have heard some reports of this and I have been taught this in training but so far I only heard third hand accounts.

No witnessing. He received an electric shock from 240 volts which threw him, while working on a washing machine. Went to hospital and was discharged. Went to work the next day. Died suddenly the following day.

[saeckereier]

What I meant was this is not some story someone told you but you knew this colleague and know that the accounts are legit?

[ma_sha1]

OK, I decided to wire the Neg. to the "-" end of the rectifier instead of 12v "-" in.
I cut the AC out wires & re-wired to the 300V rectifier tapping, this way, I can plug in a beefy AC cord for the 300V DC, so it's more safe.

There are total of 7 identical looking square power resistors & 6 of them were heat sinked to the wall, for some reason one is not. I don't know if that's some kind of negligence? As they all look identical. So I decided to heatsink it to the wall with a copper pad, as I'll be driving it pretty hard & don't want to risk one of them become the weakest link.



Biola, it's a success! I actually got a few more volts wiring to the rectifier neg.
Thanks very much for all the help!

[BoarHunter]

Where are you getting this nonsense from?

As has been pointed out any voltage high enough to disturb your heart rhythm is dangerous, potentially lethal. That includes 110 V AC.

Yes, many of us have been jolted by the mains, even 240 V, in our lives. That does not mean 240 V is safe, it just means we have been lucky.

This non sense comes from the epic argument between T Edison promoting its DC power distribution system to N Tesla promoting AC !

Note that the reason why the US did not upgrade to 220-240 AC in the fifties was also because of the safety argument.

In the EU, to reduce the risk, distribution has been done in 2 X 220 AC and 3 X 220 AC with the neutral grounded. As accidental contact is usualy between ground and phase, you get 110 and 127 respectively.
In fact it started in Germany. It allowed almost a doubling of the current carrying capacity without changing the wirings.
Better protection mechanism (differential breakers) have allowed to go 3 X 380 AC, the 220 now being between phase.

You can survive a 220 electric shock as I experienced it at age 17 while tuning a tube radio but you learn to be extremely cautious. And yes, always the left hand in the pocket, proper rubber sole, even when I use my electric razor !