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Adding a Solar Panel to the Igaro D1

Solar LeadOne of our reasons for buying the Igaro D1 USB charger was the ability to add a solar panel so that you can get the additional charge from a solar panel going through the Igaro D1 and reducing the drag of the dynamo. However with the standard setup of just plugging in the solar panel into the Igaro D1's auxiliary port the solar panel charging will only work when the Igaro D1 has turned on, which occurs only when the dynamo voltage is produced by motion. Therefore when the speed slows below 8mph or your bike comes to a halt no power goes through to the Igaro D1 from the solar panel.

However there is a hack which you can do to give motionless operation so that as long as there is sufficient power coming through from the solar panel it will charge through the Igaro D1 even while stationary. This is explained at the bottom of the solar lead page on the Igaro site here, however it isn't in enough to detail to explain what exactly you need to do. After several e-mails to Andrew at Igaro this is how I got it to work.

Solar panel modification

In order to do this modification you will need the following components and tools:

Components and materials

  • 3.5mm Mini Jack 3-Pole Stereo Headphone Plug Solder Audio Connector (you could use a mono jack instead).
  • 3.5mm Stereo Jack Chassis/Panel Socket Phono/Audio/earphone/Headset (again you could use a mono jack instead).
  • 55x35x15mm Plastic Electronic Project Box Enclosure Instrument Case (or something similar).
  • 1N4148 Signal Switching Diodes High Speed(40V+ reverse rated, silicon type only)
  • DPDT Sub Miniature Toggle Switch (DPDT = Double Pole Double Throw)
  • Some small lengths of stranded wire
  • Some electrical tape
  • Various sizes of heat shrink
  • Some small sections of plastic tube
  • Epoxy Resin glue

Tools

  • Stitch unpicker
  • Soldering iron
  • Solder and flux
  • Wire cutters
  • Wire strippers
  • scissors
  • Needle and thread

Firstly you will need to do some modification to the solar panel as you need the output to be straight from the solar panel bypassing any built-in converter or polarity protection diode (obviously any modification will invalidate any warranty on the solar panel). The solar panels we used were the Syncwire Solar Charger, 24W Dual USB Port Solar Panel. They have a very useful zipped pouch which gives access to the two USB charging points. To get to the solar panel leads inside you will need to open up the end flap and the panel that has the USB connectors. This is easily achieved as the solar panel is stitched together and I carefully unstitched it with a stitch unpicker. With the solar panels revealed I unsoldered the leads from the solar panel that went to the little box that contained the USB electronics.

DPDT Switch DiagramInstalling a DPDT Switch and lead connector on the solar panel

Due to the fact that we wanted to use the solar panel both on and off the bike and still retain the USB ports I installed a Double Pole Double Throw Sub Miniature Toggle Switch attached to the solar panel so that I could switch the power from the solar panel to either the Igaro D1 or to the two USB ports on the Syncwire Solar Charger. The diagram to the right shows a schematic of how it was connected into the system.

To house the DPDT Sub Miniature Toggle Switch I bought a very small component box off e-bay which also housed a 3.5mm Stereo Jack Chassis/Panel Socket. The 3.5mm Stereo Jack Chassis/Panel Socket was used to connect to a 3.5mm Mini Jack 3-Pole Stereo Headphone Plug Connector which was soldered to the end of the Igaro D1 Solar panel lead. By using this connector system the solar panel can be easily removed from the rear of the bike when not needed or when we wished to use it hanging from the tent at the campsite.

Fortunately the Syncwire Solar Charger has a very useful zipped pocket that could accommodate the additional component box alongside the small box that held the USB connectors. The box was fixed to the solar panel using a couple of pop rivets through the fabric and card base layer. A small piece of electrical tape was place over the ends of the pop rivets to prevent them damaging or shorting the solar panel.

Once you have connected everything and tested that the solar panel can charge through the Igaro D1 you will need to stitch the solar panel together again using a needle and some thread. To cut down on some weight I cut the flap off the end that folds over the solar panel that held it together with a bit of velcro.

For more information please look at the photos below.

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Installing the extra wire to enable the motionless charging

Solar panel additional wiring for motionless chargingTo obtain motionless charging from the solar panel to the igaro D1 you will need to install an additional wire that feeds a current from the solar panel to the Dynamo input of the Igaro D1. This current tricks the Igaro D1 into thinking it has a current from the dynamo and it switches the Igaro D1 on. You have to include a 1N4148 Signal Switching Diodes High Speed(40V+ reverse rated, silicon type only) on that extra wire to prevent any current going up the wire to the solar panel. I have drawn to the right a schematic diagram of the how the extra wire should be fitted into the system. To make everything waterproof I encapsulated the joints in epoxy resin and then covered them with plastic heat shrink.

This is how I did it:

  1. You will find on the Solar panel lead supplied from Igaro that there is a heat shrinked section where they have installed a Schottky diode.
  2. You will need to carefully cut away the heat shrink to reveal the diode and the wires.
  3. You will then need to make a cut in the Igaro power lead about 60 or 70mm below the connector that joins the igaro itself. You could put this join in the wire that comes directly from the igaro but I think it is better to put it in the power lead because if anything goes wrong it is cheaper to buy a new power lead than a whole new Igaro.
  4. You will need to measure and cut a piece of stranded wire that will reach from the cut in the solar panel lead to the cut that you have just made in the power lead.
  5. You will have to carefully un-solder the joint for the red wire on the solar panel lead on the anode side of the Schottky diode(it will be the side with the grey bar next to it). Then unsolder the join between the two black wires. You will need to do this so that you can fit over some suitably sized heat shrink (that will fit over the plastic tube) and a small piece of plastic tubing about the size that will fit over the solder joint area (due to the size of the Schottky diode I had to use a section from an old Biro pen). Then move the heat shrink and the plastic tube down away from the joint area.
  6. Solder the two black wires back together and then solder the red wire back on to the cathode side of the Schottky diode but at the same time soldering on the extra piece of stranded wire that you cut in section 3. This can be a little tricky and you will find a helping hands soldering station might be useful to hold all three wires together.
  7. When all the wires are soldered use a multimeter with a continuity tester to check that all the joints are well soldered.
  8. Bring the small piece of plastic tube up over the soldered joint area and fill both ends with some mixed epoxy resin glue.
  9. Once the glue has set bring the heat shrink over everything and shrink it with a bit of heat from a lighter flame or a heat gun.
  10. At the other end of the extra piece of wire, solder this to the anode end of the 1N4148 Signal Switching Diode.
  11. At the cut that you made in the power lead strip back the two wires both sides of the cut and then slip a piece of suitable sized heat shrink over the wire and a suitable sized piece of plastic tubing and move them away from the joint area.
  12. Solder the two black wires back together and then solder the two red wires together with the cathode end of the extra piece of wire.
  13. When all the wires are soldered use a multimeter with a continuity tester to check that all the joints are well soldered.
  14. Bring the small piece of plastic tube up over the soldered joint area and fill both ends with some mixed epoxy resin glue.
  15. Once the glue has set bring the heat shrink over everything and shrink it with a bit of heat from a lighter flame or a heat gun.
  16. You will then need to get some small cable ties to hold the extra wire to the Igaro D1 and neaten everything up.

Once everything is complete it is time to test the cable by attaching it to the Igaro D1 and the solar panel. If all is well and there is enough sunlight on the solar panel you should be getting an output from the USB ports of the Igaro D1.

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Photos Slideshow
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