Here is an easy project to start or expand your growing season...
I live in Montréal, in Québec (Canada). While we can have really hot summers, the growing season is actually short. Last year, my wife tried to start a garden planting the seeds straight into the soil in spring. After some nasty rainfalls and a noted absence of sun, we were quite lucky in fall that our survival didn't rely on our crops.
This year, we decided to use a seed starter so I created an LCD panel and a support for it.
Seriously, you should be able to tackle this project in a long afternoon if you have the tools and some soldering skills.
On the design :
I wanted something that would be "good enough" as I was on a tight schedule to realize the project and I was already quite busy. I was asked to built an inexpensive system that would be easy to assemble and disassemble.
Step 1: Bill of Materials
You will need very little stuff for this project...
- 1 (One) Sheet pan.
I bought the cheapest one from the Dollar Store. It was 2$. Go figure why it is called a "Dollar Store"... Beware: most of these pans are coated with a cheap non-stick layer that doesn't work that well on cookie but that works way too well on the adhesive backing of your LED strip. You will need to remove that coating.
- 1 (One) LED strip.
For my project, I use a 24V cool white LED strip that I found in my local electronic surplus. You can probably use any LED strip as long as it has an adhesive backing. The length is up to you and the size of your pan, but I used a 10m (30 feet) long strip.
Cool white will slow down the initial growth compared to warm white. This was a deliberate choice since I was going for shorter but stronger sprouts.
WARNING : Some LED strips are "water proofed" and have a silicon covering that is a complete nightmare to remove from the soldering pads. Just be careful not to splash water all over the light when you are watering and it should be okay.
- 4 (Four) Birch plywood, 1/8in thick, 11.5in x 11.5in
I used square 11.5 in birch plywood from a local wood supplier. It cost me 2.39$ CDN and I used one per leg.
- Kapton tape.
Easy to find on the internet from many suppliers, I don't remember where I got mine from. Kapton is ideal as it won't melt, it's quite a good dielectric (electric insulator) and it will stick to the cookie pan event if it gets hot.
Black (vinyl) electric tape is not recommended. Will it work? Yes, as long as you don't solder straight on it but prepare yourself for the whole thing to melt or stop sticking to your pan without warning.
Don't ask me how I know that.
- Electric wire
Don't go crazy. Small, multi-stranded cheap wire will work. I used red and black to make it easy to spot mistakes.
- 1 (One) Tie wrap to hold the first strip to the pan.
For the built, you will also need :
- Laser cutter
Mine is a Trotec 30W Rayjet. You can substitute any kind of cutter here as long as you know how much power you need to cut through your plywood.
You can substitute a laser cutter by a printed stencil, some glue, a steady hand and a jeweler saw.
- Glue gun
You can use simple wood glue here, and it will probably give you better results. But I was in a hurry and hot glue worked fine.
- Some clamps
Purely to make sure nothing moves while the glue sets.
- Soldering equipment
Just a basic soldering iron and some solder... Nothing more.
- Some abrasive
To remove the non-stick from the pan. I tried some 60 grit sandpaper, realized it was just taking to long so I finally just used a steel brush on a drill.
- A drill and appropriately sized drill bits
This is to drill the hole in the side of the pan for the first strip and the holes for the tie wrap.
- Something to cut the LED strip
It needs to cut clean. A sharp pair of strong scissors or a pair of pliers will do.
Step 2: Prepare Your Material
Only three things to prepare in advance : the pan, the LED strips and the wires.
- The pan
Use anything coarse to remove the non-stick coating on the pan. More easily said than done... How they ensure that a non-stick layer sticks that much to some metal sheet is a mystery (and a proprietary manufacturing secret, I was told).
You can use 60 grit sandpaper, but I used a stainless steel round brush in a drill.
It makes a lot of very fine dust. Wear a mask.
Don't breathe that stuff... It should be inert PTFE but it will be mixed with steel particles and whatever they used to stick the PTFE to the steel.
Once you are convinced that all the non-stick is gone, clean the pan.
- The LED strips
You will need to decide how many strips your pan can hold. Remember that you can only cut through the soldering pads. There is usually a black line with some scissors icon printed on the LED strip to tell you were to cut.
- The wires
Pre-cut and pre-tin all of them. When you start soldering, it will be much quicker if you have a small box with all your perfect little wires ready.
Step 3: Build the LED Panel...
This is not a soldering instructable... Nor one going through how to build an LCD panel. However, this is how you do it in four quick steps...
Prepare the pan :
Make sure you know where the center is, so your LCD strips will all line up. Use some kapton tape to isolate the end of each strips from the pan. Only put one layer, as this tape is quite resistant. You will solder on that tape and the kapton will prevent any short-circuit between your solder and the pan.
Figure out where will be the first strip and drill a big hole in the side for the strip and small holes for the tie-wraps.
Glue the strips :
Personally, I prefer to glue one strip, do the soldering, plug and turn on the light to make sure that my solder is good and that the strip is working.
Solder the strips :
First, add a little bit of solder to tin the pads. Once this is done, quickly solder a wire between two adjacent + and then between the -. Zoom on the second picture if needed. You go in a zigzag pattern to wire all the strip in series.
Protect the contacts :
Just add a layer of kapton on top of your soldered wires.
You are done!
Step 4: Make the Legs
If you have a laser cutter :
Load the wood in the cutter and set your machine for a clean cut.
On the Rayjet 30W, a power of 100% and a speed of 5% give excellent results. You may need to experiment a little at this point to get the best results.
The original design was made in fusion 360.
This is my files in two formats... The .ai file is an Adobe Illustrator file, ready to print. I also provided the .dxf files of the parts.
If you don't have a laser cutter :
Print the stencil on paper, glue the stencil on the first birch square, hold the four of them on top on each other with some clamps and pretend you are a laser cutter with your steady hand and your jeweler saw. Use some sand paper to correct imperfections (in the end, you are but an imperfect human!)
To assemble the legs...
Use common sense to figure out the puzzle. I included the final result to help you. If you struggle, ask a 3-4 years old kid to help you. Once you are happy with the construction, glue everything in place. Please, don't ask the kid to use the glue gun. They're not there yet.
Voilà, you are done!
Step 5: Final Thoughts...
I designed this to work with a Jiffy Greenhouse that I already had. However, it should work reasonably well with other products. You may need to adjust a few things, but you get the point...
I decided not to apply any varnish, paint or other protection to the wood as it was a proof of concept and I can make new legs for probably cheaper than the price of the paint...
It works really well and the pan being a very good heat conductor, it will be warm/hot to the touch but not enough to burn skin or pets.
Hope it helps some of you!