Powering Point Grey Grasshopper

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KMH
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Powering Point Grey Grasshopper

Post by KMH » Sun Sep 25, 2016 5:34 pm

I've seen several posts here (mostly Mark T I think) referencing the use of batteries to power video cameras with lower noise, even with gain turned up. I was wondering what the best way to do that is. I currently have the ac to 12V power supply that Point Grey sells, and could plug that into something like a marine battery with dc-ac converter. But I don't know how clean that ac is and it would seem to be much simpler to use a 12V battery pack wired directly to the camera via the HR25 connector. I may be missing something obvious, but is there any reason not to do that? Any advice would be greatly appreciated, as I often have poor seeing and would like to be able to increase gain more so that I can decrease exposure time.
Thanks!
Kevin



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Re: Powering Point Grey Grasshopper

Post by marktownley » Tue Sep 27, 2016 8:33 pm

Hi Kevin!

That's exactly what I do, power via the HR25 direct to my 12v battery. In terms of clean power battery is best, followed by wall wart power supplies, and worst is direct from the PC USB (no HR25).

Mark


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Re: Powering Point Grey Grasshopper

Post by Astrograph » Wed Sep 28, 2016 8:48 am

Hi Kevin

We supply power leads for the Chameleon 3, Blackfly, Flea 3 and Grasshopper 3 to let you power the camera independently. The benefits of using external power are numerous but basically;

- The power provided by the USB3 port on many computers can be borderline. It makes no difference if its a high end or a budget laptop. The first time we discovered the power problem was with a customer who used a high end i7 laptop. This caused tight horizontal lines to be visible in the image which disappeared when the camera was externally powered. Note this is not a PGR issue, it affects all makes.
- The power demands of a Grasshopper are close to the limit for the USB3 power spec so its wise to use external power anyway.
- PGR recommend the use of external power to maximise frame rates particularly if trying to use long USB cables.
- Feeding any electronic device with power from a power supply which is noisy or poorly regulated will cause it to perform worse. The audio world is full of enormous power supplies feeding small devices dealing with even smaller signals both digital and analogue. They result in huge performance gains. Apart from very obvious artifacts like the lines mentioned, obvious gain noise is reduced because the electronics operate more quietly so signal to noise is better when being liberal with the gain. This is very obvious with a colour camera.
- People go on about cooled cameras to lower read noise but the benefits of cooling a camera are lost if the electronics are noisy. This is why a specific chip does not a camera make. The 8300 chip is available in cameras at a wide range of prices. You get what you pay for and its why an FLI camera is worth paying the extra for. (the only exception being Moravian who make arguably the quietest electronics for CCD's available, but set pricing at comparatively low levels). PGR already make cameras that are known for low noise but powering externally just takes them a step further.

PGR cameras can be powered with a range of voltage but the cables we make use a 2.1mm DC socket which is common for 12v supplies. In principle a good quality switch mode PSU would be the best supply as these are very quiet at video frequencies. A battery supply is the most practical if in the field. However any are an upgrade over a noisy PC supply.

Cables are £26, £14 and £36 made up for Blackfly, Chameleon 3 and Grasshopper 3/Flea 3 respectively and on my website.



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Re: Powering Point Grey Grasshopper

Post by KMH » Thu Sep 29, 2016 2:51 am

Mark/Rupert,

Thanks for the information- I will definitely give this a try.

Kevin



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