Level 1 => Radio Gear => Topic started by: Phil_G on January 10, 2013, 21:43:20 pm

Title: Frsky V8HT bind-board alternative
Post by: Phil_G on January 10, 2013, 21:43:20 pm
A few people have asked about this so I thought it might be worth posting.

The standard Frsky V8HT bind-board is quite aptly named. It really can be a bind to fit, especially with their unnecessarily thick and rigid wiring. Due to component placement variations, no two are exactly alike, so a template doesn't always work out, and you cant really bend the LED as it stands on three sturdy wires.

On a recent Skyleader Clubman conversion using another V8HT the donor transmitter had a convenient and unused shrouded button intended for the trainer facility,  and a transparent meter through which an LED could be arranged to shine. 
I decided to ditch the bind board altogether, and wire a new LED and the existing 'trainer' button in its place.
The LED is a 3-wire component, basically its two LEDs with their cathodes (negative) connected together. They're readily available from such as RS, Rapid etc: [link] (http://uk.rs-online.com/web/p/visible-leds/2285685/?searchTerm=228-5685&relevancy-data=636F3D3126696E3D4931384E525353746F636B4E756D6265724D504E266C753D656E266D6D3D6D61746368616C6C26706D3D5E5C647B337D5B5C732D2F255C2E2C5D5C647B332C347D2426706F3D313426736E3D592673743D52535F53544F434B5F4E554D424552267573743D3232382D353638352677633D4E4F4E4526)
Note the three different lengths of the leads - this identifies the internal connections, red , green & common:



Now, Frsky use some strange colour conventions in their wiring. Negative (common to the LED and one of the two button contacts) is red. Yes, on the bind board connections, neg is red. The red LED is connected by the black wire, and the green LED is via the yellow wire. The green wire is the other button contact:



For now, lets just ignore the logic of this colour scheme    $%&

You can common (ie connect together) the two negatives either on the button contact, or on the module. I wouldnt common them on the LED as its quite fragile. If the LED and button are to be mounted close together, then common them on the button. If they are well separated, then common them on the module. Electrically it makes no difference:


To make the connection you can either snip the Frsky wires to an inch or so, then solder the new wiring to whats left, or you can do as I did and remove all the horrible standard wire as that makes a much neater job. Use 3-wire ribbon for the LED (servo cable will do nicely) and 2-wire for the button (strip two wires from same servo wire)


If you're doing the same on the PPM connector, note that the Frsky order doesnt match standard servo cable. On the module it goes pos, neg, signal (ppm) as can be seen from the label.  Servo cable goes neg, pos, signal - so you have to cross-over the pos & neg:


Remember that by removing the original PPM wiring you've also removed the Schottky diode, so ensure that your conversion includes that component somewhere in the PPM wire, banded end to the encoder, non-banded end to the module. My encoders have a PPM schottky built-in so no worries there.

For anyone wanting to do this, you can use the original LED if you remove it carefully, but its easier to use a new one. You can use more logical colours for the cable, red is the red-LED, black is common neg, and white is green-LED (as a famous fat bloke once said, 2 out of 3 aint bad).


Maplin part number is CH09K @ 99p
RS part number 228-5685 @ 33p   (who says RS are expensive?)   
Rapid part number is L-93WEGW @ 24p

Remember, its a common-cathode type we need.

For the pushbutton, any small panel-mount momentary-action button will do the job, eg Maplin FH59P @ £1.69
If you can find a smaller one, all the better. A shroud would be good.

For the wiring, you can use the thinnest, most flexible servo-wire as its carrying very little current, but do support the joints with heat-shrink tubing.

Here's an example:


The result is a much neater installation, much easier to do, and which takes up much less room inside the tx case.
What would be absolutely spot on for the job would be a small red/green illuminated button, they do exist but they're ridiculously expensive.
Title: Re: Frsky V8HT bind-board alternative
Post by: singlechannelman on January 10, 2013, 23:35:35 pm
Thanks Phil I am sure I will use this method in the near future it not only will look better it sure makes wring a lot simpler to do.
Title: Re: Frsky V8HT bind-board alternative
Post by: Geoff Sleath on January 14, 2013, 13:26:46 pm
This is a sensible mod.  When I made the conversion module for my Mux3030 I broke the LED in the process of trying to make it shine through the hole I'd drilled in the case and had to replace it with one I bought from Maplin.

I'll be glad when the Frsky transmitter becomes available - promised for the New Year, hopefully that means this year now :)

Title: Re: Frsky V8HT bind-board alternative
Post by: Phil_G on April 07, 2013, 22:16:07 pm
For some time now I've been struggling to finish a really tiny 2ch propo 'project' transmitter for my smaller gliders, and I'd intended using the original V8HT 1way module.   I keep losing interest in the project so some time has passed and now, as V8's are no longer available I'd prefer a 2way DHT - but its so small that fitting everything in is a real challenge.  If I'm very careful fitting the case together, there is just enough room to cram in a 2S 500mah lipo, the encoder with no pins, and a disrobed DHT.
The bind board is a problem though.

So this got me thinking about the DHT bind board and just what is necessary and what isnt. The DHT bind board is quite a bit more complicated than the V8HT.    I concluded that:
1) We dont absolutely need the LED to indicate power-on.
2) we dont need the LED to indicate bind mode and low-power mode, because the module beeps.
3) if the transmitter will only ever be used with 2way receivers, we dont need the toggle switch.
4) the only essential is the bind button!

Heres the original layout which I traced from a DHT:

and heres the 'bare essentials' version which is much easier to fit in a cramped space:

Please note that I haven't actually tried this idea yet but I'm sure it will work just fine.

You can see its a bit of a shoe-horn job.  The stick unit is a Futaba (thanks RobC!)
The toggles are for digital trims, there wasnt enough room for mechanical trims so I had to remove them!
The last pic has the bits just stuffed in to show where they will fit, hopefully!