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12V down to 7.4V (Buck converter?)

diensth

Apr 27, 2012
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Hello.
Am I in over my head on this one? Would really appreciate someones help!
Let me explain as best as I can. Learning as I go..

I am wanting to power my video camera and video monitor from one single battery that I have (Rolux Li-on 14.8V 8.8ah 130Wh)

I have a a few batteries that came with the camera and a few that came with the monitor.
(Camera: sony a7s - battery "7.2V 7.7Wh(1080 mAh) min 7.3Wh(1020 mAh)"
(Video Monitor: SmallHD 501 - LP E6 Battery "7.2V 1300mAh 9.4Wh"

I have a "Dummy Battery" for each device. My current set up is that I run the dummy batteries through a battery bank (2 battery banks, one for camera.. one for monitor)
Battery bank = XT-Power 10000mAh/37Wh Output: DC 9V/12V (you can switch)

I have always run my Camera dummy battery (no voltage regulation) through the 9V dummy battery.. no problems..
I have now purchased from ebay mini 360 DC-DC buck converters (specs at bottom) and ran one inside my monitors dummy battery (multimeter says the dummy battery/monitor is getting 7.8 volts)

Run through the XT-Power battery bank at 9V the monitor runs perfectly fine.. but when switched setting to 12V the monitor shuts down after a minute..
I am guessing the buck converter is getting too hot and cant handle it and shuts down? unable to find out how hot.. but when power is running through the buck converter gets very hot to the touch

My overall issue.. If the monitor cant handle the 12V running from the Power bank.. then i know that I will be unable to use my ideal power supply (the Rolux 14.8V 8.8ah 130Wh Battery)
Is this Buck converter just not the tool for the job? seems as though..

Looking forward to help on this!
Johnny~

Buck converter specs:
Module Properties: non-isolated buck - Rectification: synchronous rectification - Input voltage: 4.75V-23V
Output voltage: 1.0V-17V - Output Current: lowering the value of 3A, long 1.8A - Conversion efficiency: 96% (maximum)
Switching Frequency: 340KHz - Output ripple: 30mV (no-load) - Load regulation: ± 0.5% - Voltage regulation: ± 2.5%
Working temperature: -40 ℃ to +85 ℃ - External dimensions: 18 * 12 (L * W )mm
 

BobK

Jan 5, 2010
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The buck converter should not run significantly hotter whether the input is 9V or 12V. Some of these boards state a maximum current, but require a heat sink (not included) to reach that max. Check with the seller.

Bob
 

diensth

Apr 27, 2012
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Thanks Bob.
Yes, it is very hot to the touch.. and i will be needing power for long hours on end.
This was a cheap purchase from china. I don't have my faith in them to say the least..

Is there such a thing as mini buck converters that do not require heat sinks?
If so then I believe that I would like to purchase another type of mini buck converter online from someone more reputable and never mind these ones I have now.. Thoughts?

I am really wanting to keep the build as small as possible - keeping all electronics enclosed within the small dummy batteries. No air ventilation inside the plastic enclosure.. perhaps this is an issue as well?

Johny~
 
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diensth

Apr 27, 2012
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Maybe I improperly wired up the converter.. causing it to overheat and shut down on me?

The image attached.. I wired the positive in to the "IN+" and the negative into the "IN-" and then the negative out from the top left "OUT-" and the positive out from the bottom left "OUT-"
Did I do this wrong? Why are both OUT's negative, shouldn't one be positive?
 

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BobK

Jan 5, 2010
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One of the outs should have been lablelled +. If you simply guessed, you are lucky you did not destroy your camera or monitor. You should check the polarity with a meter to see which is + and which is -.

Can you post a link to fleaBay offering for this board?

Bob
 

BobK

Jan 5, 2010
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Also, you have not told us how much current the monitor requires. The board seems to have a limit of 1.8A, and, if it is really as efficient as they say, it should be able to handle that current without a heat sink.

Bob
 

diensth

Apr 27, 2012
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Here is the front of the board.

I did check the polarity with a multimeter Bob - this is how I determined the Volts that came out. I just wanted to ask why it is labeled as such.

What are you asking me to post Bob? I don't know what FleaBay is. Below is a link to the board I purchased.
http://www.ebay.ca/itm/5pcs-Mini-36...-Down-Module-4-75V-23V-to-1V-17V/152217140877

I don't understand how to figure out how much current the monitor or camera requires. If you could please help me with this. I know that the battery which powers the monitor states "7.2V 1300mAh 9.4 Wh" Can the current be determined through this info? If not then how do i determine this.. Through the use of a multimeter?

Thanks for the link Davenn! I was actually considering this one below. same specs i believe.. but smaller form board which is important to me. It doesn't state DC-DC anywhere.. but perhaps that much is obvious..
In the "Ask a question" portion of the page I have asked if the board has heat issues and if it gives noise to a video signal for my monitor and camera.

http://www.flyingtech.co.uk/electronics/mini-step-down-voltage-regulator-output-08-20v#comment-3628

Thanks for much everyone!
 

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davenn

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The board seems to have a limit of 1.8A, and, if it is really as efficient as they say, it should be able to handle that current without a heat sink.

it's supposed to be able to do 3A continuous

I did check the polarity with a multimeter Bob - this is how I determined the Volts that came out. I just wanted to ask why it is labeled as such.

I gave you that answer

I don't understand how to figure out how much current the monitor or camera requires.

look in their manuals ... of you don't have them they are most likely available online

Thanks for the link Davenn! I was actually considering this one below. same specs i believe.. but smaller form board which is important to me. It doesn't state DC-DC anywhere.. but perhaps that much is obvious..

it does, actually, in several places, in big bold letters ;)

In the "Ask a question" portion of the page I have asked if the board has heat issues and if it gives noise to a video signal for my monitor and camera.

OK ... no response as of yet ?
 

diensth

Apr 27, 2012
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The ebay link you sent me stated DC-DC yes.. but i was referring to the link i put up.. cant seem to find it saying DC-DC..

Looking at the monitors website.. they state:
"recommended Power Supply LP-E6 coupler with built-in 7.2v, 2A regulator"
"Overload Protection - yes"
"Voltage 6.0 - 8.4 volts"

My camera requires 2.1 Amps or more.

Where does this leave me? I need a board that gives at least 2.1 Amps to be used for each device.. and its alright if 3 amps come into the device? I hope my question makes sense..

No response as of yet on the question that i asked on the website.
 

davenn

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but i was referring to the link i put up.. cant seem to find it saying DC-DC..

as with my link, yes it does ... in big bold letters and in several places ;)



My camera requires 2.1 Amps or more.

is the buck converter supplying both the camera AND monitor or just the camera

either way, looks like you really need one rated at 5A .... you are NOT going top get one in the small profile that you want
the board IS going to be bigger

here's a link to a 5A version .....
http://www.ebay.ca/itm/5PCS-XL4015-...874486?hash=item3ac452f636:g:wc4AAOSw6btXRYCt

and its alright if 3 amps come into the device?

only the current required by the device will go into the device .... a power supply ONLY supplies what is required


Dave
 

BobK

Jan 5, 2010
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Here is what the link says:
lowering the value of 3A, long 1.8A
Whatever that means. Another add for what looks like the same board says 1.8A continuous, 3A max.

The datasheet for the chip says 3A continuous, but it probably depends on the thermal design.

Bob
 

diensth

Apr 27, 2012
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Here is what the link says:

Whatever that means. Another add for what looks like the same board says 1.8A continuous, 3A max.

The datasheet for the chip says 3A continuous, but it probably depends on the thermal design.

Bob

Ahh yes.. that makes sense.. certainly not going to use the Boards that I have now. Thanks
 

diensth

Apr 27, 2012
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as with my link, yes it does ... in big bold letters and in several places ;)





is the buck converter supplying both the camera AND monitor or just the camera

either way, looks like you really need one rated at 5A .... you are NOT going top get one in the small profile that you want
the board IS going to be bigger

here's a link to a 5A version .....
http://www.ebay.ca/itm/5PCS-XL4015-...874486?hash=item3ac452f636:g:wc4AAOSw6btXRYCt



only the current required by the device will go into the device .... a power supply ONLY supplies what is required


Dave

Both the camera and monitor will be running from the one 14.8V battery from separate outputs off the battery. I wanted to put a Board in the cameras dummy battery.. and a 2nd board in the monitors dummy battery.. but you are saying that each board cannot be 3 Amps and I must use one rated at 5 Amps?

Just to clarify.. are you saying that only the device will only take in the current that it requires? If you give it 5 Amps then it will only take 2.1 Amps? Thanks :)
 

BobK

Jan 5, 2010
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You do not give a device 5A. You give it a voltage, it will take as many amps as it needs at that voltage. This is why a night light does not explode when you plug it into an outlet that can provide 15A.

Bob
 
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diensth

Apr 27, 2012
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Ahh yes.. the two of you have helped me a great deal. Thank you very much again :)
 
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