Not satisfied. :)

An AC charger should output the correct DV voltage to charge the battery. So why would anyone need a "voltage converter?" I think your description may be missworded. Did you mean they use a Converter from the AC Charger to the Varizoom in place of the battery?

The part you describe sounds good -- if the 8.4V is not too high. And if 600mA is adequate.

Nope! As strange as it may seem, they use a 12v charger with a converter to the 7.2v battery and another converter to go from the 7.2v battery to the 12v monitor. When I got it, I was befuddled. Can send you pictures if you would like. Very inconvenient, adapters everywhere! A simple 12v battery would have saved a lot of hassle!

Mike

Another solution would be to use a voltage regulator IC. They are cheap, normally below $1 dollar and only require a couple of capacitors to make work (well they really don't even need those truthfully). They have specific ratings and you should be able to find one in the 7.2V range.

Assuming that the camera has internal regulation to deal with slight variances of at least +- 1.0v, 8 volt regulators are available such as the LM2940

http://www.national.com/pf/LM/LM2940.html

A couple of these in parrallel should work or a more complicated circuit could be built for exactly 7.2v with a variable voltage regulator

Wow! Seems like cost wasn't a factor.

The VR IC is what you can get at Radio Shack.

Adjustable-Voltage Regulator LM317T
Model: LM317T | Catalog #: 276-1778

Want options for your output voltage? This regulator has an adjustable range from +1.2 to 37VDC.

Features

Type LM317T
Case Style: TO-220
Maximum Output Current: 1.5A

Under $3!

The problem with cheap voltage regulators is efficiency. In stepping down the voltage they generally do it using by dropping the voltage is across a resistor, wasting all that power in dissapeated heat. A 14v->7v adaptor may throw away 50% of the battery.

The other problem is current. 1.5A @ 7v isn't going to cut it for the HD100.

The IDX converter sounds like it uses a high efficiency voltage converter from the run times the camera achieves. These converters can often achieve 80-90% efficiency.

PS: Connecting these devices in parrallel is a bad idea. A fundemental electrical engineering concept is not to connect the output of one device to the output of another in such a way unless you integrate some form of protection circuitry.

Sorry -- that's not how these circuits work. Totally solid-state.

This was just a part you can pickup for $3. An electronics store can help you find a 2.5A part.

check out their efficiency though, many of them still suck. They still throw a lot of the power out over diodes. I have one of those cigarette lighter voltage regulators and using it a 14.4v BPL40 could only power my 7.2v DV301 (10W) for about the same time as the battery natively powers my DV500, which consumes about 20W.

Then look at high efficiency voltage regulators like the ST L296. Still only a few $ iteam but they require a decent set up circuit to function properly but achieves up to 90% efficiency.

Not all voltage regulators are created equal.

Some IC based voltage regulators are notoriously inefficient.

However some are based on buck converter design which is highly efficient (over 90%), and contain the necessary smoothing circuitry to avoid output noise.

Here's an example specifically designed for LiOn applications although I don't think as high as 12V...
http://www.semiconductors.philips.co...A1208T_N1.html

There's also the LM5642 rated @ 15 amps in single channel or 30 amps in dual channel @ 2.5V - you can divide that by 3 for 7V output application.. if we assume the camera draws about 17 watts at 7.2V then you are going to need a device rated at roughly 2.5 amps (I=P/V)... although you probably want at least 3amp rating for safety. So this *should* do the job and you can design in overload protection etc...

Finally here's a product that could work already built....
http://www.powerstream.com/dc-3318.htm

Note the non-isolated ground..

Maybe someone with superior engineering skills could chime in here as to the suitability of this for the purpose. It's only about 78% efficient but that's not too bad and it's relatively cheap.

1) Curious where you found the current rating as I couldn't find it.

2) Looks like one side can deliver, at 7.5V, 5 amps which is 2X what's needed. Which means the otherside can be used for another voltage. However, according the notes, tying both halfs together outputs cleaner power.

GOOD FIND!

By the way, the LM150 can deliver 3A and uses far simpler circuit. You can find specs and many designs at:

http://www.national.com/ds/LM/LM150.pdf

This might also be available at Radio Shack along with the other parts. Don't know it's efficiency, but when powered from a car I'm not sure I care that much other than it might get hot. I'd get the flat package and mount on the outside of a tiny metal box.

I found the current rating here:

http://www.national.com/diagrams/refdesigns.cgi

I would say looking at that the current rating really does depend on the other components used.

That TEA1208T; "High efficiency DC/DC converter" has only got current supply capabilities up to 0.42A, no where near what we need.

The ST L296 can supply up to 4A with a efficiency a bit over 80% at about 2.5A. They cost me less than US$4 each but the cost of the inductor for the circuit was much more :-(

http://www.alltronics.com/download/L296.pdf

Steve might also like to note how many resistors are inside these 'solid state' devices (eg http://www.national.com/ds/LM/LM150.pdf as detailed above), supporting that my origonal statement about the efficiency of many of these devices is low due to the use of resistors to split voltage rails. Its a simple effective approach, just not efficient.

Using a component like the LM150 I would not advice at all, since all the voltage drop is been transfered into heat. Very inefficient for battery operation.
I would only go for DC-DC operation. For a DC-DC device you need to take at least twice the Amp available on the specs.
Because otherwise you will have a rimple on the DC output which could cause audio noise and strange audio frequencies on the internal audio circuits.

Since these DC/DC circuits work with switched circuits around 500KHz. These output cables work as antennas. Therefore the length of the converted DC output must be a short as possible to reduce audio hiss internally in the camera and interference with wireless mics. An EMC coil on the output cable also helps.

Quote:
Originally Posted by John Mitchell
There's also the LM5642 rated @ 15 amps in single channel or 30 amps in dual channel @ 2.5V -- you can divide that by 3 for 7V output application.

Looks like one side can deliver, at 7.5V, 5 amps which is 2X what's needed.

According the notes, tying both sides together outputs cleaner power and would provide 4X the needed current.

There is a low frequency (about 200kHz) and a high-frequency (about 400kHz) version available. Looks like these will work, but you do need a number of external components.

I think I found the solution, the Swit or Varizoom adapter S-4100A/S:

http://www.varizoom.com/battery/s-4100a.html

That only works if you are running off mains...