Pokeys LED driver for Flyengravity sixpack (and others)

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jodo
Posts: 13
Joined: 25 Jul 2011, 19:29
Location: Germany (southeast of EDDF)

Pokeys LED driver for Flyengravity sixpack (and others)

Post by jodo » 04 Sep 2013, 22:52

I know this is not the perfect forum for cockpit builder electronics. But I profitted a lot from this forum during Prosim's early days, its evaluation phase and still now after becoming a registered user. I think the time has come to do my bit and that's a cheap universal LED driver (I wonder why Ian hasn't published something similar on his highly valuable site).

It started with buying two Flyengravity sixpacks. While waiting for the parcel to arrive I wondered how it would be possible to connect it to my already existing cards, two Pokeys and a Phidgets card. Mechanically, the sixpack is a nice piece of workmanship. However, I found out by reading through several forums that the electronics are less perfect. The LEDs are wired common cathode opposed to many interface cards (like Phidgets or Wendy's Pokeys extension) which are wired common anode. Another problem is the dual LEDs are connected in series which means these LED pairs need a different supply voltage. I searched several forums but no ideas but buying expensive cards, resoldering the LEDs etc.

The Pokeys card is able to drive a few LEDs directly, but the current is limited.
Here's a simple and cheap solution for those who can solder and still have a couple of Pokeys outputs left.

Parts required (the whole stuff is below 10 Euros):
1 x Strip board, 50 mm x 100 mm or smaller (0.75 EUR)
4 x 18-pin IC sockets (0.30 EUR)
4 x 8-pin pre-wired connectors with pin strips for in and out connections (2.60 EUR)
1 x 2-pin pre-wired connectors with pin strips for 5 V supply (0.30 EUR)
6 x Resistor 220 Ohms, 1/4 W (cents only)
2 x UDN 2981 A source driver (4.70 EUR)
Solder wire
1 x calm hand when soldering (beyond price)

Here's an image of the board.
Image

The circuit is powerd with 5 V DC. Each UDN2981A is triggered by up to 8 Pokeys outputs and delivers enough current to drive 8 LEDs, LED pairs or even relais etc. I used two additional IC sockets to hold the 220 Ohm series resistors for the single LEDs of the Flyengravity sixpack. The dual LEDs are connected directly to the IC outputs (slip a piece of wire into the socket for these). If you want to drive LEDs other than the Flyengravity sixpack you can easily adjust the LED voltage to the required values by replacing the resistors –- simply slip them in and out of the IC sockets. Of course, you may also solder them directly to the board.

You can add 10k pull-down resistors on all inputs of the UDN2981A. But these are only required if you want your LEDs dark until Pokeys and Prosim are fully fired up. I don't care so I left them out which saved me further 32 solder points.

Enjoy it or ask me if you need further information!

Best regards,
Jochen

golfromeo516
Posts: 1
Joined: 16 Sep 2013, 07:25

Re: Pokeys LED driver for Flyengravity sixpack (and others)

Post by golfromeo516 » 16 Sep 2013, 08:04

Thanks for this great post.

I'm wondering if the LEDs could simply be removed and "rotated" to alter the common Cathode to common Anode state of the engravity 6 pack?

Also, could the resistors simply be "wired" in rather than having to build this board?

Excuse my simple questions (in every meaning of the word!).

Cheers
Tony

mickc
Posts: 1004
Joined: 29 Aug 2012, 12:11

Re: Pokeys LED driver for Flyengravity sixpack (and others)

Post by mickc » 16 Sep 2013, 08:23

golfromeo516 wrote:Thanks for this great post.

I'm wondering if the LEDs could simply be removed and "rotated" to alter the common Cathode to common Anode state of the engravity 6 pack?

Also, could the resistors simply be "wired" in rather than having to build this board?

Excuse my simple questions (in every meaning of the word!).

Cheers
Tony
They can be rotated, i did this on mine, and changed the LEDs while I was at it, as they come with yellow LEDs and the 737 uses amber for caution lights.
( I use Phidget LED64 cards)

Jochen's idea is great for those using Pokeys for LEDs, and I like the idea of easily changeable resistors :) 10/10 for innovation !

jodo
Posts: 13
Joined: 25 Jul 2011, 19:29
Location: Germany (southeast of EDDF)

Re: Pokeys LED driver for Flyengravity sixpack (and others)

Post by jodo » 19 Sep 2013, 07:58

Also, could the resistors simply be "wired" in rather than having to build this board?
Tony,
Sorry for my late reply, I just returned from holidays.
If your question means to wire the resistors to the sixpack and drive it by the Pokeys card, the answer is no. Pokeys has a limited current for driving LEDs directly ("you are limited to driving the led with 4 mA and a maximum of 100 mA in total").

However, I must admit, mickc's idea of just rotating the LEDs is even better as long as you don't mind disassembling a newly purhased product (but that's normal for cockpit builders, isn't it?).

Cheers,
Jochen

onthefence
Posts: 415
Joined: 19 Jan 2013, 19:04
Location: Marathon, ON, Canada
Contact:

Re: Pokeys LED driver for Flyengravity sixpack (and others)

Post by onthefence » 14 Feb 2014, 18:30

Hello Jochen,

I was wondering if you might have more pictures and information on this project. It looks very interesting however my electronic skills are not so great. For instance I sourced out a driver ic UDN2981AT. Does that T on the end make a big difference or will this chip work as I can't seem to locate a UDN2981A? Do you happen to have more pictures of the board connections? Thanks for your trouble.


Ed
Best wishes,
Ed
FSX-SE,PS737,JS2,FSUIPC4,WideFS,ProAtc/X,RAAS Pro,ASN,vPilot,PFPX,TOPCAT,PSU,Accu-Feel,Rex4 Tex Direct,GSX,C1-W10 i7@ 4.9, C2-W7-i7 920,C3-W10-P4,FDS CDU,CPFlight EFIS/MCP EL,OC MRadio
Image

jodo
Posts: 13
Joined: 25 Jul 2011, 19:29
Location: Germany (southeast of EDDF)

Re: Pokeys LED driver for Flyengravity sixpack (and others)

Post by jodo » 16 Feb 2014, 11:36

Hello Ed,

I am sorry but couldn't find a data sheet on the T-variant of UDN2981A. I guess this T has nothing to do with the basic functions so it should do for this application (I 'm not sure though).
However, if you haven't done such things before (electronics, soldering etc.) I recommend you don't do it or better disassemble and resolder the LEDs with switched polarity to use with a phidgets card instead of building such a board. It's also a bit fragile regarding power supply (I recently blew one of my two UDN2981A somehow, perhaps because of oscillation). So there might be the need to add condensers as high-frequency filters on the supply voltage. You may recognize it can be even more complicated in detail depending on your setup.

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