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DC/DC converters

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Anybody know where I can buy (on-line) a Traco TEN-3-0512 converter, or the equivalent? I have not been able to find a distributor.

This is a 6V to 12V module.

Are there any issues with running my 75Mhz Rx on 6V? I have read that it may impact servo life. Anything else?

Thanks!

Tom

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There will be a slight increase in servo current draw (Rx current will remain the same). The increase in servo current is put to good use though (faster travel and more torque).

Be sure that the supply can handle the servo load. Do not under estimate the requirements. Plan on several amps to handle the peak currents. Many of the better 6V R/C VRegs are rated for 5 to 10 amps.

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This Traco converter was recommended by one of the KAP (Kite Aerial Photography) guys to power both radio Rx and video Tx. It is only rated at 250mA, however.

Believe me, I'm not challenging the Gods on this, but I seem to remember reading that

a 40 in/oz. servo will draw 40 to 60 mA while working (no load), and around 10 mA at idle. Did I misread this?

There are step-down and step-up converters. They both have around the same efficiency ratings (72 to 82%, typically). Assuming you start with the same battery power in either case.....say 1500mA battery, will the battery last equally as long in both situations (stepping up from 6V to 12V, or down from 12V to 6V)?

Tom

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I seem to remember reading that a 40 in/oz. servo will draw 40 to 60 mA while working (no load), and around 10 mA at idle. Did I misread this?

Servo idle is typically about 10mA. No-load currents from an standard (not high torque) servo can range from 150mA to 200mA. Moderate loads will double that. Heavily loaded or stalled standard servos can draw up to 1 Amp peak. Hi-Torque servos will draw more at a stalled state. For absolute safety, you should plan for a full servo stall state.

A model with five moderately loaded servos will usually experience peak currents that exceed several amps. If the servos are high torque or digital, the currents will be higher. That is why decent 6V R/C regs are rated at 5 amps and higher.

Assuming you start with the same battery power in either case.....say 1500mA battery, will the battery last equally as long in both situations (stepping up from 6V to 12V, or down from 12V to 6V)?

Assuming the same battery type and mAH rating, the step down buck regulator will offer slightly longer battery service. This is due to the lighter load on the battery (mAH capacity is affected by load currents).

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For info, my digital Hitec HS5945MG servos draw 2A when stalled (at 6V). With digital servos the peak current is often also attained when moving with no load, as they apply very strong accelerations at both ends of their movement to be faster. Not for a long time of course.

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It has occurred to me (duh) that since I'm going from a 6V battery, and converting to 12V to power the video Tx, that my radio (servos) will be getting their power directly from the battery, not from the ceoverter, so the servo draw becomes a non-issue.

So, back to my original query.....can anyone offer a source (vendor) for the 6 to 12 converter?

Tom

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Assuming the same battery type and mAH rating, the step down buck regulator will offer slightly longer battery service. This is due to the lighter load on the battery (mAH capacity is affected by load currents).

Actually, won't the battery last almost twice as long when stepping down from 12v to 6v?

Without going into the math, a 12v, 1500mah battery stores twice the power of a 6v, 1500mah. Assuming similar efficiency between your step up and step down converter, you should see twice the runtime... unless I misunderstood the question?

Regards,

Bill

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Actually, won't the battery last almost twice as long when stepping down from 12v to 6v?

Good point. I just assumed that part was understood. I was describing the fine details: the stepped-down DC-DC switcher method will require lower battery currents which can extend the useful mAH of the pack (vs. high currents due to a step up method). But as you say, approx 2X runtimes will be experienced with the 2:1 step-down choice.

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I found the highly acclaimed PT5041 mentioned mentioned on several of the cam project pages.

In case you missed the new VReg Primer: http://www.rc-cam.com/dc-dc.htm

The VReg's impact to the battery's current are discussed there in detail.

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WOW.

Great informations guys!

I have my homework assignment, thanks.

The enclosure on my pan/tilt has limited space in which to hold a battery pack.

It holds a 9.6V pack perfectly, but the video Tx signal is unstable when the servos are working. When I switch to 12V, the noise goes away, but a 12V battery pack won't fit in the enclosure.

I need to do some life testing. I need to get 4 hours of operation for both the radio Rx and the Video Tx. The servos (2, 40 in./oz., and 2, mini) will only be used sporadically, but the video signal will be on all the time. I may need to go to an external battery for this kind of performance.

I am using a battery grip on the camera, with 6, 2400mA "AA"', so this should be able to go the distance.

Remember, I'm only running a .5 mA video Tx, so power consumption will be on the lower end of the scale. .......and with the servos sitting at idle for most of the time....?

One thing seems for sure....the video Tx wants 12 volts, and nothing less....period.

Tom

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I meant to say that the video Tx power is .5mW (not mA).

I realize this whole deal is hard to follow, so I am (attempting) attaching an image of my rig. Now you can see what I mean about the enclosures. The right side case houses the video Tx, switch, LED, recharge jack, and aux. power jack. In other words, there's a lot going on in that space. The 9.6V battery pack fits in there just perfectly so I'd really like to stay with that, but my video Tx say NO.

You can see the mini servo that trips the shutter on the Nikon 8700. I also have another mini that works the zoom controls on the back of the camera.

Remember, this is a SURFACE application.

I hope the image comes through...if not I'll try again.

Tom

post-6-1101014991_thumb.jpg

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I need to get 4 hours of operation for both the radio Rx and the Video Tx.

What is the current draw of the Video Tx?

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Don't know. I'm guessing 250mA or even less. This is based on numbers I have read for much higher powered transmitters.

I have a Keithly meter that will measure amperes.....I'll put the probes to it and find out for sure.

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