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General summary of the documentation:

the parts shown in grey are still under construction.

The aim is to provide additional information for the layman. By design, this photovoltaic solar cooker is intended for self-builders. Experienced professionals, craftsmen or technicians manufacturing cookers with a view to marketing, will kindly bear with the abundance of details given below...

We are talking here about a cooker operating with a panel of 375 W max / 40V max / 10 A max, but all other cooker power ratings are conceivable provided that all the rules of the art are respected, particularly with regard to the electrical characteristics of the various components, and provided that, for safety reasons, they do not exceed 40 Volt.
The fourth part is devoted to more general information on electricity, components, the photovoltaic panel, etc.
The web links listed below are commercial links provided for information only, and their continuity is not guaranteed; however, these products are commonly used.

A) The cooker base

Exterior grade plywood is made with moisture-resistant glue, so it's a good choice for the cooker. 8 mm plywood is easy to cut with a fine-toothed hand-saw. It is advisable to always mark the cut with two lines to make it clear where the cut is to be made, and to specify which side of the cut the waste is on.

How to saw with a egoine saw

To prevent the egoinic saw from stubbornly deviating from the line assigned to it, "Leave the index and middle fingers extended, so as to keep the blade and forearm in the same axis" (Xavier Buhot-Launay - "Construire un bateau en bois"; a model of pedagogy ! ).
All plywood must be painted or stained.
After pre-assembling for test purposes, if possible, use glued and screwed joints. 3x20 screws work very well. To assemble a piece of plywood on a wooden cleat, it is always preferable to drill the plywood beforehand (diameter 2 or 2.5 for a 3 mm screw), and to countersink the location of the screw head with a 90° countersink.

B) The control panel

To supply the thin sheets that will hold the console components, all solutions are acceptable. You can also supply PVC sheet, for example from Polydis.fr, sheet thickness 3 mm code PVCC3W04..

scroll saw

To make the cuts, you can use a Bahco 302 scroll saw, ref 63813414 at Leroy Merlin. A DIY cutter can be used for finishing if required. Alternatively, you can machine the sheet using a small table-top CNC machine, or make the parts on a 3D printer.
It is preferable to supply the electrical components (switches, etc.) before making the cuts, because of the possible changes in dimensions.
N.B. If you have any problems with the supply or manufacture of small, thin plates for a one-off build, you may contact contact@cuisson-solaire-photovoltaique.org.

supply of switches
Good quality switches are essential for two reasons. Firstly, in the case of the photovoltaic cooker, the current intensity, also known as amperage, is relatively high, up to 8 or 10 Ampere (while the voltage does not exceed 35 or 40 volts). To transmit this amount of electricity, it's essential that the switches have good contacts, otherwise they heat up (which consumes electricity ! ) and can be destroyed by heat, not to mention the risk of fire.
Secondly, we're talking about direct current (DC) here, not alternating current (AC) as is usually available on electricity networks. One of the peculiarities of direct current is that it causes a flash when a circuit is broken, when the current is 'cut', resulting in premature wear and tear of the contacts. Any switch that heats up should be eliminated. Switches available on the Net at very low prices should be rejected.

main switch

Three-position main switch, panel cut-out 30 x 22mm, flat terminals 4.8mm: for example at conrad.fr reference 700045 - 62. The third position allows the available electrical current to be sent to another use, such as recharging telephone batteries or "USB" lamps when the cooker is not in use.

little swtich Resistor control switches with two "2 x Off/On" positions, panel cut-out 19.2 x 13 mm, clip terminals 4.8 mm: for example from Conrad.fr, ref. 1587538 - 62 or 1587540 - 62 . The "2 x Off/On" specification is important, in order to duplicate the power supply circuit and therefore reduce the flash.

Wattmeter supply.
On an Asian website, search for "wattmeter 0-20 A, 6.5-100 V DC", or directly with the reference PZEM-031.
wattmetre The cooker operator only takes into account the power in Watt to adapt the number of ceramics in operation, taking into account the sunshine at the time. haut de page

Console wiring.
Use flexible cable according to the H07V-K standard. The K specifies that it is a flexible cable, a U would indicate that it is a rigid cable, unsuitable for our use. Regarding the soldering of electrical cables, many tutorials are available on the Net.
Electrical connections can be crimped or soldered (or both!). Isolate connections with of the heat-shrink tubing; after installing a small piece of sheath on the weld, just heat it slightly with a lighter.

C) The heating block

Aluminium sheet.
5 mm thick, which is a good compromise between heat transfer and rigidity, is essential.
If the sheet is sheared, make sure that it is not bent very slightly, which would make it unsuitable for our use. If you're lucky, you may find a sheet of suitable dimensions from a scrap dealer on the Internet, in which case a jigsaw cut is perfectly feasible (make sure there's no vibration on the saw), and the 142 mm diameter doesn't have to be perfectly rounded.
A good solution is to go to a laser or water jet cutting workshop, but these workshops don't usually handle such small quantities.

To mark out the holes, you can use this template in A4-.pdf format. Download it here, look for it in your downloads, and print it. Download . Check the dimensions with the two 100 mm lines. Then fix the template to the heating plate, and drill directly through the paper with the centring drill.
If you have a CNC machine at your disposal, download the plan in DXF format here (it will appear in your downloads) drawing DXF With a small desktop CNC, it's very easy to "point" the holes before drilling them again.
N.B. If you have any problems with the supply of aluminium sheet for a one-off project, you may contact contact@cuisson-solaire-photovoltaique.org.

Once the drilling, milling and deburring have been completed, carry out two checks
- a visual check: place a ruler on the plate and use a light to check that there are no gaps between the plate and the ruler.
- a tactile check, by running your fingertip over the entire surface to spot any burrs.

Some thermal considerations
The thermal conduction λ of aluminium, i.e. its capacity to allow heat to pass through the material, is 230 W/m.K. The thermal conduction λ of air at 100°C is 0.031 W/m.K. Whatever the units here, the ratio is 230/0.031, or 1:7420. A layer of still air 1 millimetre thick insulates as much as ... 7.40 metres of aluminium. This shows just how important the flatness, good surface finish and cleanliness of the hotplate are for the transfer of heat between the hotplate and the cooking vessel: the slightest air gap compromises the operation of the cooker. (For the sake of completeness, it should be pointed out that air can also transmit heat, but in this case we are talking about masses of moving air, convection and not conduction through the material, which is not the case here).

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Fixing the ceramics and assembling the heating block

Belleville washer

- Belleville spring washers: obtain washers with a diameter of 4.2 inside and 8 outside. See for example: otelo.com 67881793, or vis-express.fr 3552170051 (available in quantities of 30)

Gower washer

- Grower washers M6: for example otelo.com ref. 67881943 ,or vis-express.fr ref. 8751000618

fan washer

- Fan-shaped washers are available from the shops listed above, or from DIY shops.

banana plug

- banana plugs, for example Radiospare ref. 175-8974 , can be used to connect the cooker to the solar collector, replacing the domino.

For the supply of PTC ceramics, please refer to Part 4.