Remote page turner using simulated touch

[aconicq1]

I have been really keen on a remote control for a long time and until recently there was no real clean solution. Now there is a solution with promise using OTG. For more info see KindleLazy at https://www.mobileread.com/forums/sho...d.php?t=278776.

Here I add to the now mostly redundant and odd solutions with a crude 'simulated finger touch' solution that uses no programming.

This solution requires soldering as well as a reed relay, and acts to give a wired remote which is connected to the screen using a clip and allows for a page turn to be simulated. This solution is really low-level, only allows page turns in one direction, and can be applied to any touchscreen kindle, touch, paperwhite, etc (or capacitive touchscreen i.e. mobile phone).

Spoiler:

List of items
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- 2xAA battery holder case
- tactile switch
- two core wire (i.e. speaker wire. Here called extension wire ~1.5m long or as desired)
- aluminium foil
- thick plastic card (i.e. old ID card)
- short length of thin copper wire
- superglue
- reed relay
- medium side bulldog clip

Background
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To simulate a touch on the screen you need a reed relay, in particular a NO SPST 3volt reed relay. This means it is normally open (NO, i.e. it is in the open state when not operating), single pole single throw (SPST, just means it has only one switch inside, a SPDT can also be used), and 3v are very quiet when they 'click' closed compared to the 5v I tested and can be operated with less power. Reed relays work by using magnetism from a coil to close the contact on a switch when activated. The closing contact will then complete a 'main circuit' between the screen and the battery's negative which will simulate a touch on the screen.

Procedure
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Step 1: Glue the tac switch onto the battery holder. Cut little grooves or drill holes for the wires to enter the battery holder. Wire up the battery holder, the tactile switch and the extension wire so that when the tac switch is pressed the wire gets 3v from the batteries.

Step 2: solder a small wire on the relay to join one side of the 'main circuit' to the negative of the reed's coil.

Step 3: solder the extension cable to the positive and negative (with the wire from step 2) of the reed's coil.

Step 4: solder a short length of thin copper wire to the other end of the 'main circuit'. It is really important that there is not too much wire used here as too much capacitance in the wire and aluminium (next step) will simulate a screen press by itself.

Step 5: fold several layers (4-6) of aluminium foil into a small rectangle (1cm x 1.5 cm) and have a single layer extending as a tongue from this to attach the wire.

Step 6: superglue reed relay and foil onto a cutout of the plastic card (3.5 cm x 1.5 cm). Attach wire from end of reed relay to aluminium foil tongue.

Step 7: hold contraption onto egde of kindle (preferably in landscape mode) using bulldog clip. Do not let metal from the clip touch metal on the reed relay/foil.

Step 8: change margin defaults in koreader so that text is not being hidden. I set the 'large' page margins to be (1=10, 2=10, 3=50, 4=10) which works well in landscape.


Considerations
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- Tac switch press duration: holding down the tac switch continuously turns the page. The switch must be held down for long enough that the reed relay is switched (i.e. enough volts hit to trigger it) but quick enough that the relay is triggered only once. Sometimes two pages will turn which is annoying, sometimes no page turns. Perhaps a switch debouncer would help this.

- Amount of metal (wire + foil) before reed switch which acts as capacitance store and falsely simulates a press. Just taking a long wire it is possible to get the touchscreen to respond without earthing the end of the wire. Try use as little wire and foil as possible.

- Size of foil footing which is in contact with the screen: using a finger only a tiny surface area is needed to simulate a touch, yet my tests show a rectangular 'foot' about 1x1.5cm to be the smallest which still reliably works. Ideally a thin strip down the edge would be better so as less screen is wasted with margin, but this doesn't seem to work for me. Also you might need a bit of padding (pushing the foil away from the plastic card) to make sure the aluminium foil is properly touching the screen.

- Wireless: the whole thing can be made wireless with a wireless receiver and transmitter but power then needs to be supplied to the reed relay side as well as the transmitter side.

- Debug: if you are not sure where the issue is check if the reed relay is getting current when the tac switch is depressed. Check if the reed relay is switching by listening for a small 'tic' or by measuring resistance on the 'main circuit'. Physically touching the foil or the wire connecting to the foil should cause a page turn. If it does not then there is either too much wire/foil or the foil foot is not cleanly on the surface of the screen.

- Solid state device: I did test a solid state relay, which are much smaller, but as there is no physical separation in the switch it did not seem to work for me on the sensitive touchscreen.

Overall it is a little fiddly and requires some finessing until it works well. It seems the amount of current in the capacitive screen changes over time and over power downs. So sometimes twisting or moving the device seems to affect how well it page turns. I highly recommend that KindleLazy be explored first as the solution here does not work with 100% accuracy. However, without any other remote page turner, this is great and means you no longer have to move your arm to turn the page, just a quick tap on the remote.

Pictures here: http://imgur.com/a/Nr87N

[knc1]

The "basic touch" (KT, KT2, and KT3) are not capacitive touch screens, they are all the IR scanner touchscreens.

Note the thickness of the bezel around the screen.