Let me start off by saying I am in no way an engineer or electronics pro; merely an amateur/DIY-er and High School Physics & Biology teacher. I enjoy building things in my off time to both bring better scientific inquiry into my classroom and build my overall background knowledge of various subjects.
Currently, I am trying to scale down a hydroponic system to an all-in-one, single plant hydroponic growing system that runs on a AAA NiMH 1.2v*850mAh and is trickle charged by a solar cell. I hope to keep this set-up as SIMPLE as possible for my Freshmen & Sophomores to build w/o much knowledge on electricity/circuits.
BELOW is the current/iteration set-up w/o battery and PV cell
My first iteration of this prototype came from the plans found here and after asking a question on this board about running the PV cell directly to the pump was met with some frustration by both myself and the user who was trying to help (to which, if you are reading this; I apologize for not having the information you needed at the time but after much work, I think I have the required info!).
The voltage put out by the PV cells is fine, but due to the current needed to kick over the pump, I would have needed several PV cells in parallel just to get it started which then would run the pump at an unnecessary current (nominal voltage) and would have issues running on cloudy/low light days. So I ditched possibility of adding a few (3-7) thousand microFarad capacitors in-line; I would try something else...
The current iteration is to have a single, rechargeable AAA (open to ideas) run the 4.8VDC vacuum pump (open to ideas) while being trickle charged by a PV cell (one of the following below):
- 60mm x 80mm: SUN - 1.5V @ 0.246A ~ Indoor - 0.9V @ 0.0015A
- 136mm x 110mm: SUN - 6.8V @ 0.21A ~ Indoor - 4.8V @ 0.0012A
- 130mm x 150mm: SUN - 5.5V @ 0.375A ~ Indoor - 4.1V @ 0.0025A
I have soldered a 1N914 blocking diode inline with each positive wire from the PV cells above and all work properly. The circuit diagram I was trying to follow can be found here and the schematic is below:
Ultimately I am replacing the 1300mAh battery with a smaller one to keep the project simple enough and keep the pump running at a slower, steady rate. The pump I am using can be found here.
So I soldered two additional leads to a AAA battery clip and put in the rechargeable NiMH AAA 1.2V @ 850mAh (See Below)
This battery runs the pump at right around the speed I want it to, but I have no way of knowing if the solar cell is trickle charging the battery, let alone which of the aforementioned solar cells would be the best to hook up to the extra leads to the battery terminal.
At this point, I am at a stalemate with my electronics & engineering knowledge. I will take suggestions, constructive criticisms, ideas, etc. on how to get this project up and running efficiently. Keep in mind I am hoping for the simplest setup for students with very little electronics knowledge, but I am more than happy and willing to go the extra mile for them in doing any pre-PCB building/soldering if necessary. Your help and guidance is greatly appreciated!