Building a Simple Electrical Heater - Part 2

Recent additions - electrical heater box and growlight panel, both on test

I've put this on a separate post to my original, because the whole design has now become a little more complex !

After building the two identical electrical resistance heating elements, I spotted a 6" (150 mm) 24 VDC fan at our local car boot sale a couple of weeks ago.  This was snapped up for £2.  

the fan....

With this addition, I thought I could maybe improve on my original free-convection idea and wire up this fan in parallel to our two heating elements, to push the air over the heaters.

Growing Palm Trees from Seed ...

My wife has always wanted a palm tree in our garden.  Despite my insistence that this is bloody-freezing Northern England and therefore it's just not possible, I've had to endure the accusing glances and disparaging comments whenever we've driven past other local gardens in which, admittedly, many appear to be flourishing.

Our nearest garden centre also stocks several of them, but they're all under the protection of the glasshouse areas and not standing out in the open ground.  The smallest versions are more than twenty-five quid each and they even want around £300 for some of the larger specimens !

Anyway, we were on holiday in scorching-hot Mallorca in early August, and on one of our many trips out and about on the hired motorbike we passed a Spanish garden centre and stopped for a browse.  

Making a LED Growlight Panel

This is another build for the greenhouse electrics.  Growlights.

I've been reading up a bit about the light requirements of plants.  There's a lot of very technical stuff out there, but basically it seems that blue-ish light is best for seedlings & green vegetative growth and red-ish light for germination, flowering and fruiting.  

One of the many images from a Google search on the subject of plant light
requirements.  Unfortunately, this was one of several in a wide ranging
cut-and-paste job, and so I don't have the link for an acknowledgement....

Since the plan is to supplement the available sunlight in the winter when we start off the leeks and onions etc, then mostly blue seems the order of the day with just a splash of red.

It gets even more technical when they start talking about specific individual wavelengths within the blue and red regions for optimum growth, e.g. 439, 469, 642 & 677 nanometres, but blue is blue and red is red as far as I'm concerned - there must be at least some of the light emitted that touches on these optimum wavelengths.

Building a Simple Electrical Heater

This is following on from my recent post on the greenhouse solar installation.

To use any excess panel energy available during the cooler months, I've built electrical heating elements to connect directly to the 'dump load' circuit from the charge controller.  There are no proprietary heating elements available for the power and voltage I require, and even if there were then they'd likely be prohibitively expensive.

The first job was to source some suitable resistance wire.  Lots of types available on eBay but not too many which are insulated, so I opted for enamelled 0.7 mm diameter Isotan wire (aka Konstantan) available from a seller in Norway.

The reason for buying insulated wire was that it could be formed either in or around metal pipe or ducting.   In the end, I opted for inserting it in small-bore copper tubing, a coil of which I had lying around the workshop.  

However, this wasn't the only choice for the design - I'd originally envisaged simply wrapping the insulated wire around the outside of a 22 mm diameter copper pipe, but I didn't have any to hand and B&Q wanted £17 for a 2 metre length....

I unrolled the small-bore copper tubing coil and measured its length at 7.2 m.   A few basic calculations were carried out to establish the heating power available from the lengths of tube and wire I had.