jaymen

R/C Bob sent me a FrSky DIY conversion with a 2.4 GHz Rx.
So we dug out a '68 Heathkit "Digital 5" and have it in the ICU under conversion surgery. My twin 8 year old sons will learn to fly on Bonner sticks. Pictues will follow.

pchristy

I converted this Ace MicroPro about a year ago:



I'd always fancied having a go with single stick, and was lucky enough to salvage this brand new and unused example from being thrown in a skip!!! The FrSky hack module went in easily, and has so far provided an absolutely rock solid link:



The single stick has proven very easy to get used to, but what has thrown me is the throttle! 40 years+ of having it under my left thumb makes it tricky remembering its now under my middle finger instead!!!

BTW Jaymem, on the subject of Bonner, and knowing of your expert knowledge in the field, can you explain to me just how the Digimite servo amp works? (The original 8-channel one). I've been renovating my Digimite 8, and its all working except two servos. Probing around with a scope shows that the feedback pot appears to adjust the amplitude of the reference pulse, not its width! I have a very bad photocopy of the circuit diagram, but am struggling to understand what's meant to be going on in there! I know its more "analogue" than "digital", but making sense of it is proving hard!

Best of luck with the Heathkit project! That FrSky stuff is magnificent!


Pete

iflyj3

My Feedback: (7)

Pete,

If you are not a member visit http://groups.yahoo.com/group/mp8k/
and https://sites.google.com/site/mp8kinfo/

With level 7 EPROM you can move the throttle under a different finger easily.

pchristy

Hi Dan, and thanks for reminding me! Yes, I am a member over there, but haven't visited for a while!

I actually quite enjoy the "cuddle-box" method of flying, and am determined to learn to do it properly! And, I'm making far fewer mistakes now than when I started using it, but I don't feel confident enough to tackle helicopters with it just yet!!!

I've got three 8Ks in total, one on 459 MHz (legal here in the UK) which uses a series 3 rom, the single stick (series 4) and another twinstick, currently without an RF module, also series 4. I really ought to update them, but "if it ain't broke, don't fix it!"



BTW, I hope I haven't committed a faux pas with the images! I couldn't figure out how you guys manage to embed small ones that magnify when you click on them. Every site seems to have its own "magic formula" for images, so I just used the method I'm familiar with....!


Pete

HighPlains

My Feedback: (1)

Great, I have a PCS 5 channel that also has the Bonner sticks I might like to convert. Circuitry should be very very close to the early Heathkit, chicken meet egg. It's a complete system with receiver and 5 KPS-7 servos, but somewhere along it's travels, it got a non-stock antenna connector.

For those who have never held a transmitter with a Bonner sticks, they are incredibly poor by today's standards. The spring centering is so stiff it is possible to fracture the bones in my thumbs and stress the tendons. The trims move the mechanical centering of the stick, and the travel of the sticks is only something like +/- 15 degrees, so if you were to put in full up trim you have less stick travel left. You also have to push the trim lever in to move it, to otherwise forcing it will damage the trim. I suppose that since people were used to just flipping switches for control, they thought they had to make new proportional fliers work for it.

jaymen

Got it installed, but it jitters the servos. I found the frame rate was 16msec, so I added a couple caps to the multi and got it to 21 msec. In another thread on this, someone suggested that since it was for 8 channels, it needs a longer frame. I am in th process of building a 5 volt LM7805 regulator and driver circuit to get a 5 volt pek to peak PPM modulation signal, positive going pulses. Have yet to try out these mods, still soldering......

I beleive the Bonner servo amp converts pulse width to a voltage, and this voltage drives the servo amp just like an analog type. The pulse transformer converts the pulse width to a varying pulse amplitude on it's secondary. Thus the pulse amplitude will vary with pulse width, and longer pulses give more pulse amplitude and vice-versa. This pulses peak DC voltage is then rectified and filtered into a DC voltage which is compared to the voltage on the feedback pot. I have a good schematic, but no PDF scanner, give me some time to take a photo and post it.
Jay

jaymen

Got it working great, well not on the first, or second, but on the third try.

The inverter doodad w/ onboard regulator I built needed a pull down to ground to properly load the open collector stage on the Heathkit encoder.
Then the signal levels were a perfect TTL level with nice square positive going PPM pulses.

I hooked up the module next and the receiver bound, so I plugged in a servo and it twitched,, went crazy, and the receiver lost bind.
Then, the LED on the Tx FrSky module began to flash erratically and the module made whinning sounds that would come and go, and then the LED would stay on solid.
Guess what? My batteries had died! So I charged them and got out a spare pack to proceed

I found it quit gliching/twitching with a seperate battery for the FrSky module, but running two battery packs would be impractical,
so the next modification was to put the multi back to 16msec, and then run the encoder off the regulated 5 volt supply. This fixed it, no more twitchy servos, yes!

You have to recalibrate the encoder because at lower voltages (5 volts) the neutral pulses shift to about 1.7msec, and the frame rate decreases, theerby making the frames longer. It's no big problem and easy to fix by tweeking the pots on the encoder, or adjusting the stick pots.

I like this set-up and plan to do more as I have a bunch of cool vintage Txs, like the ill fated Micro-Avionics XL, and an older PCS that will look great out at the field. I may even hack my Orbit, who knows?



Jay

ukengineman

Pete,

PM me your email address and I will send you a clean circuit of the Digimite servo. I recently restored my F&M Digital 5 and that had some duff servos.

Alan

iflyj3

My Feedback: (7)

Alan,

If you don't mind, please send a copy to me also. I have a Digimite 8.

Thanks,

wb4guk (at) aol.com

pchristy

Jaymem,

A while back I converted an old World Engines transmitter for a friend using a FrSky module. Ideally, the FrSky wants to be driven with an open collector NPN down to earth. If you are driving it with a signal that is pulled up to the +ve rail, a Schottky diode in the signal line works wonders!

I had a lot of jitter problems with the World Engines system at first, but then noticed that the original modulation was done by an NPN transistor in the emitter leg of the oscillator transistor. I simply removed the original oscillator transistor (a good move anyway!) and connected the FrSky signal line to the now open collector of the modulator transistor! Result: A perfectly clean signal, and a happy friend!

Thanks for the description of the Digimite amp. I'll have another look at it in the near future! I've been lucky enough to get my hands on a couple of very scruffy, non-working, Digimite servos, so I have some to rob for parts!

Cheers,


Pete

pchristy

Alan, thanks for the offer! Have PM'd you.

Some of my other old radios:

A Grundig tuned-filter set (1965) still working perfectly!


The Digimite:



And a Sprengbook (designed by Doug Spreng during his time in the UK):


All in good working order, except for a couple of Digimite servos! But, no! I'm not converting them to 2.4 GHz! I have some home-made receivers for the Digimite and Sprengbrook which mean I can use the transmitters without risking "museum piece" airborne packs!


Pete