Hiya @Scrungee , thanks again. No light meter I’m afraid. Fairly sure light output is rated at 500watts total, fwiw. I’ve just checked the lighting (plugged it in) and discovered one of the four units doesn’t work, so needs replacing. Only trouble is, I don’t have a clue what it is Any idea? It’s around 1ft long, overall.
It’s ok @Scrungee , I’ve tracked it down, it’s one of these... 125w 200w 300w CFL Dual Light Bulb Red and Blue Hydroponic Grow Tent Swiftair (125W): Amazon.co.uk: Garden & Outdoors
Looks like a 105w cfl lamp 105 cfl grow light - Recherche Google EDIT: Crossed posts, @Freddy Do your CFLs hang vertically, or are they fixed horizontally? As it might make some difference to u/s of lights to growlight box base height, but if the former would enable simple adjustment of cable drops.
I've installed a LUX light meter app on my phone and will check against my light meter, then edit this post. EDIT: Installed and readings taken for comparison, see follow up post below.
Meanwhile I really need to get a wiggle on, seed sowing time fast approaches. This weekend I need to get started with assembly of the ‘box’, so here’s my ‘plan’. The mat measures 75 x 40cm’s, so I’m thinking the ‘box’ needs to measure something like 1m x 600mm to allow for foliage width. As @Scrungee mentioned insulation, I’m thinking 25mm polystyrene to line the inside, bottom and sides. Mylar on order...
Been reading your thread and its made me think of cobbling together a cold frame with heat and light. Heat from soil warming cables under sand bed plus thermostat . Outside insulation from cold water tank jackets being sold by b&q for 89p today. Some tin foil inside to reflect the led lights. Heavy fleece to protect from frost. This will be outside as i dont fancy the risk of burning down the house with my shoddy electric wiring Btw radiator reflective panels 3.50 in b&q today.
Your lights appear powerful enough to illuminate an area larger than the heating mat. I find it useful to have illuminated but non-heated space to move seedlings into that needed heat to germinste, but then rewuire far less warmth to grow on.
I installed Lux Meter (Light Meter) free from the Playstore (by My Mobile Tools Dev), then tested my 2 growlight setups by turning on lights at least several minutes before taking a reading to enable them to get up to full output, starting app and placing phone on its back on the growbox base with face/display facing up (it uses the front facing camera metering, the one that faces you as you view the screen) and waited briefly for it to reach its final readings. It appeared to be good enough to check an approximate distance under the lights where the illumination would be the same as sunlight. App light reading 12,499 LUX, light meter reading 17,000 LUX. The app meter reading is more like what I was expecting, and oddly when I took readings at the perimeter of the growbox (not directly under lights) they were both around 11,000 LUX which is my target. App light reading 11,153 LUX, light meter reading 11,450 LUX
Ok, so it would probably be worthwhile making the box a bit bigger. I’ll aim for around 1.2m x 600mm. My only concern would be that light levels might be a little low at the ends as the lighting is concentrated centrally, but nothing to lose going bigger. Once put together I’ll install a light meter app and see what transpires. Thanks so much for going to all that trouble, you’re a star
My cordless just ran out of juice, so while I wait for it to recharge I thought I would show progress so far... £65 so far on materials
Not just for that plywood I hope! I get great 8 x 4 foot sheets of the stuff for free off the sheeted free pallets I collect for stove fuel, and my battens all come from skips. (I'll restrain from making comments about your possible method of providing bottom heat to that box).
Just one rather large sheet of plywood @£21, the rest on 21x21 timber, insulation and some hardware I’ve just had a thought, how am I going to feed in the cable for the mat? How big a hole do I need @Scrungee ?
Cables, power supply to mat + sensor connection to thermostat. The sensor cable can easily have a hole drilled for it after the box has been completed, but the power cable might be a bit tricky as you may not know where to position it until the mat arrives and you're able to check the connection location. Personally I'd be reluctant about dismantling the thermostat to be able to feed a cable end into the box. A workaround could be a small rectangular hole in one of the sides adjacent the connection point of a size large enough to feed the thermostat through from the inside, then screw a small, notched plywood panel to cover the hole. That would enable removal of the mat whenever required and permit relocation for use elsewhere outside the box. My thermostat would require a minimum size 80 x 110mm hole, and the sensor a 6mm dia. hole. The power connection to my mat is in a corner, on the long side of the mat 80mm in from the corner, but these may all vary. Who did end up buying from?
