Far rev switch

Like B&Q for homebrew radios
Post Reply
chlluk
Posts: 87
Joined: 19 Feb 2018, 15:38

Far rev switch

Post by chlluk »

Hi all
Is there such a thing as a forward reverse bang bang switch that can be driven from a proportional channel, just like a pair of relays to carry enough current to drive a Mitsubishi servo motor.
Clive
Tobe
Posts: 665
Joined: 16 Feb 2018, 06:19
Location: Varberg or Stockholm, Sweden

Re: Far rev switch

Post by Tobe »

Why not use a large servo with the rotation stops removed like they do in robotics?
Cheers,

Tobe
chlluk
Posts: 87
Joined: 19 Feb 2018, 15:38

Re: Far rev switch

Post by chlluk »

Hi all
Sorry for the spelling on previous message spell checker does its own thing.
What I had in mind was a method to help me use up my large stock of original servos.
I have looked at fitting modern electronics but in many cases the feedback pot requirement can be a show stopper. I wanted to emulate the Grundig variation filter
That has two small relays one for each direction. It could be built into a tiny unit like the GG recorder and fitted inside the servo. Reeduino would be ideal to provide the bang bang command.
I could use all my climax servos and belamatics , makes the flight pack look great
Clive
chlluk
Posts: 87
Joined: 19 Feb 2018, 15:38

Re: Far rev switch

Post by chlluk »

Further on the topic,just reading another forum stream from someone who needs to do same thing. He said to use standard servo amp ,set feedback pot to centre position (stick mid point) and glue feedback pot. I can replace servo motor with
belamatic motor. Off to workshop to see what happens.
User avatar
Phil_G
Posts: 597
Joined: 15 Feb 2018, 23:32
Contact:

Re: Far rev switch

Post by Phil_G »

I've made reeds servo drivers using two of these micro-relays:
https://uk.rs-online.com/web/p/products/4227013/
They're really tiny, standard 0.1" spacing and not too expensive.
A pic senses left/neutral/right and switches relayA/neither/relayB respectively.

rs_relay.jpg
User avatar
RON
Site Admin
Posts: 613
Joined: 12 Jun 2017, 15:09
Location: Stokesley North Yorkshire

Re: Far rev switch

Post by RON »

Phil
Is this what you use for your thingymejig range tester lighter upper thingy.
Sounds brilliant. I’ll have to make one, but maybe a deluxe version with real high brightness halogen bulbs that are just bright enough to light the estate up :D

Ron.
G0MBV Class A Radio Amateur, North Yorkshire
User avatar
Phil_G
Posts: 597
Joined: 15 Feb 2018, 23:32
Contact:

Re: Far rev switch

Post by Phil_G »

Just to emphasize how tiny these relays are, here's a new 5p coin:

rs_micro_relay.jpg

I had wondered about doing a PCB for the reed servo board but never got around to it.
It would be two of these relays, two npn trannies and a pic. The relay coil needs 30mA which
is too much for a pic output, I pondered (but didnt try) two outputs paralleled per relay instead of
transistors, which would make a PCB even simpler... and yes, its pretty much the same pic
code as the range-test indicator thingy. If you're averse to pics then an attiny85 would do the
same job...

Re the LEDs, they're only 0.2" ultras but at night can be easily seen a mile away Ron Image


chlluk
Posts: 87
Joined: 19 Feb 2018, 15:38

Re: Far rev switch

Post by chlluk »

Hi all
Just back from the shop have reeduino driving a bellamatic. Balanced the feedback pot over neutral posn without trouble. Do like the concept Phil has described with micro relays.
Clive
chlluk
Posts: 87
Joined: 19 Feb 2018, 15:38

Re: Far rev switch

Post by chlluk »

Hi Phil
Have you described the servo drive board in any of your articles or docs. I could remove the amps from my bonner transmittes and wire them old style as duramites.
Clive
Pchristy
Posts: 413
Joined: 16 Feb 2018, 13:57
Location: South Devon, UK

Re: Far rev switch

Post by Pchristy »

One word of warning: Bellamatics are intended to run off 2.4 volts. A modern servo amp with a bridge output will deliver 4 volts or more to the motor (assuming a standard 4-cell pack). Not sure how long a Bellamatic will last under those conditions....

Tobe's single function actuators are very similar to a Bellamatic, and should handle 4 volts OK. No slipping clutch, so you would need to current limit the stall condition, though.

A better bet might be a very early style amp (Microtrol?) designed to use a centre-tap battery - as used in the early 4-wire servos. Or use the bridge amp to switch separate output transistors and use a centre-tap?

I like Phil's micro relays! In keeping with the original, and should be easy to concoct a drive circuit for them...

--
Pete
Post Reply