I have received a basic design for a motion-capture camera trap to capture insect pollinators in the field visiting orchid flowers. It will need to run from a battery source possibly for days rather than hours. I wish to use a c-mount camera and lens. The lens will need to operate in macro for close-up images. Is either of the available lens better for this application and is either of the powerbank with a USB output preferable for longer operation?
Derek
Hi Derek, welcome to the forum!
I can’t speak to the choice of camera or lens but as far as USB powerbanks go there are only a few things to consider.
Some powerbanks will only supply power if they detect a minimal load, Raspberry Pis are pretty thirsty as far as microcontrollers go, so it’s unlikely your Pi will have problems for drawing too LITTLE power 
You will need to decide which Pi you will use, as they vary in how much current they need. The power needs are listed here.
Once you know the maximum current draw to expect, check that your power bank has a continuous current rating higher than that.
The powerbank will have a capacity in milliAmp-hours, to find out how long your batteries will last you can divide the capacity by the instantaneous current load, to get the duration.
For example:
Good luck with the project!
Hi all
Most power banks specified mAhr capacity is for the battery, ie; at 3.7V. You have to convert to mWhr then back to mAhr @ 5V to get a realistic number. Then multiply by the conversion efficiency to get the ACTUAL capacity. I have a 15000 mAhr (quoted) power bank which states on it that that is the battery capacity and I have measured the approximate real figure (Using a Ruideng AT34 USB Tester) is about 11000 mAhr. Also while these devices are fine for charging phones and other devices the 5V is not very clean and switches off at about 100mA so is unsuitable for powering most small electronic bits.I think far better off with battery and boost converter. Use the power bank to charge the battery by all means but may not be too good directly powering some devices.
Cheers Bob
Good catch, I have done this in the past for my own projects (my battery banks use Wh). I omitted this for simplicity but it will make a noticeable difference… I’ll blame Friday arvo brain-drain for that one.
Forgiven
Cheers Bob
Would a PiJuice HAT and additional larger battery be a more appropriate approach?
Bit hard to comment without knowing how much current you need and for how long.
I would not mix supplies. I doubt that a hat will be enough. I think they are more for a UPS when the power fails. If you are talking days continuous I think your battery will finish up quite large. Then if your peak current is substantial a boost converter may be your next problem. But before any further consideration I think the forum needs to know your requirements. So far we have a C mount camera and lens. Not even a camera type.
Cheers Bob
I am a little unsure what you require other than as best I can see a Trent’s chart a Raspberry Pi 4 B 600mA. To run in the field for 1 - 2 days (24 - 48 hours).
Raspberry Pi High Quality (HQ) Camera https://core-electronics.com.au/raspberry-pi-hq-camera.html Raspberry Pi 6mm Wide Angle Camera Lens (CS-Mount)
https://core-electronics.com.au/raspberry-pi-6mm-wide-angle-lens.html
and/or
Raspberry Pi 16mm Telephoto Camera Lens (C-Mount) https://core-electronics.com.au/raspberry-pi-16mm-telephoto-lens.html
I see no information regarding additional power requirements regarding the camera so have no idea what that would add to the 600mA for the RPi 4 B.
I have no idea if there is different power usage when the design is waiting to be triggered against recording an event.
Hi Derek
That is what is needed. I am not familiar with RPi stuff but 600mA seems reasonable. You are right about the camera. They keep this sort of spec a bit of a secret but I wouldn’t think it would be too much. Someone out there may have measured this or must know. Unless the lenses are motorised they will not use anything.
I am only guessing but I would go along with about 1 Amp until I found out better. You should allow some “fudge factor” so even if total turned out to be only say 700mA I think you should allow for a minimum of 1 Amp.
48 hours, that equates to 48 or say 50 Amp/hrs. Getting up there.
The next step is deciding on battery chemistry and voltage required. I assume everything runs off 5V.
Having decided on battery how do you charge it.
Do you leave the camera in situ and bring the battery to charge or do you bring the whole thing in to charge and only deploy when required. That will probably help in deciding batty type.
Cheers Bob
HI Bob
Thanks that is all helpful. I am not trying to invent something completely new, these thing exist and I have been involved with projects in the field when they were used. I have the basic design provided to me but I wish to make sure it is using current purchasable components including the better camera.
How long I can get it work in the field for will be what is reasonably practical rather than any absolute. They would be left in the field only for the life of a battery charge and then collected and recharged back at base/home.
The Low Current Lithium Ion Battery Pack - 2.5Ah (USB) https://core-electronics.com.au/low-current-lithium-ion-battery-pack-2-5ah-usb.html may be a starting point.
I first need to assemble the RPi and camera etc and get that working on the bench then consider battery options then knowing its power requirements.
RPi zero is a consideration for lower power consumption but I do not know what other limitations that would present.
This RPi is all a new learning experience for me as it will be my first actual Raspberry Pi project.
Hi Derek.
Good idea Get something up and running first then you can actually measure the required current. If you have an adjustable bench power supply this may be more convenient than a battery and would probably have V and A meters built in. whichever, heading in the right direction.
Cheers Bob
Thanks Bob.
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