Escapement driver from PWM

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Scott Todd
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Joined: 26 Mar 2018, 23:21

Escapement driver from PWM

Post by Scott Todd » 05 Dec 2019, 02:04

This may have been answered and Phil probably already has something but I couldn't find it. I want to put an original escapement in a small model and control it with modern RF/receiver. I want to do the whole rubber band thing :)

Can anyone help with a small circuit to take the PWM (?) signal from a modern receiver and turn it into the On/Off to control a classic escapement? I realize its kind of like turning AC to DC and back to AC again but it lets me use the simplicity of Phil's PIC encoder or an Arduino and a modern RF module and receiver to fly an actual escapement.

I really want to play with these actuators I picked up from Internet. There is probably a better place to post it but this is a little foam board airplane I test all my radio stuff with. It started life as a Flite Test Tiny trainer and has evolved over several iterations to suit me. It weighs 7 ounces. It uses a 250 size quadcopter motor and a 5x3 prop. Anything from a 300-800 2S or 3S lipo flies it great. Its a total blast. If I lived near a slope, I would have a round nose version ;)

It may need a slightly fatter fuse to contain the small escapement but I can whip one up and have it ready to fly in an hour or so.
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Wayne_H
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Location: Temora, NSW. Australia
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Re: Escapement driver from PWM

Post by Wayne_H » 05 Dec 2019, 02:54

Hi Scott,

You can use a switch designed for switching on and off auxiliary functions - this is but one example:
https://hobbyking.com/en_us/dr-mad-thru ... ?wrh_pdp=3

However, it's worth repeating the warning Phil gave me several years back - The switch is purely for escapements. Actually I would strongly recommend you leave the escapement idea to one side for a while, call that plan 'B' and go with the emulation. Fifty-year old escapements just aren't reliable enough and I'd hate to see an accident caused by a sticking escapement - we live in litigious times and a claim could be expensive. The whole point of the 2.4g S/C project is that its exactly the same experience but absolutely 100% reliable - which an escapement can never be.

I have several escapements and will eventually fly one just to be able to say "I did it", but it's hard to go past a modern servo rigged with a torque rod to emulate the escapement's operation - that I have done and it works beautifully :D
Cheers,

Wayne
Once a Retrobate, always a Retrobate............ ;)

Scott Todd
Posts: 66
Joined: 26 Mar 2018, 23:21

Re: Escapement driver from PWM

Post by Scott Todd » 05 Dec 2019, 03:17

Thank you Wayne. Why didn't I think of that? I might actually have one somewhere around here.

I have been modeling for 50+ years. I fly everything from Turbine Airplanes, Turbine Helicopters, Scale, Race, Pattern, IMAC, to park foamies. There are 185 models hanging all around my 3300 sq ft house that are ready to fly. Once I get an idea, I usually bird dog the snot out of it until I'm satisfied.

I'm all about safety. I want to play with Escapements but I didn't say anything about flying it Single Channel ;) (yet) I have converted over 30 old metal box radios using Phil's sketch and Arduinos. I enjoy playing with the S/C emulation but always have the stick and throttle to fall back on. Whatever gets an escapement will still have traditional throttle. If I get good at it, I may brave an electric single channel foamy but it would have a throttle timer on it like the modern glider competitions use for timed climbs. I'll post back when I get something going.

belli
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Joined: 19 Feb 2018, 19:19

Re: Escapement driver from PWM

Post by belli » 05 Dec 2019, 06:15

Hi Todd,

I have a few mechanical actuators too and wish to do the same as you. The original 'switch', Graupner, etc, are based on a 358 op-amp. It is just an integrator, very simple but also very slow, not really suitable for a mechanical actuator. The newer Hobbyking versions are probably based on a micro and would be much faster with a bit of de-bouncing too. It might pay to buy a few and see which are best.

I am not sure if one of the members here offered a PIC or Ardrino based version which would offer the faster response and maybe a bit of de-bouncing, there was some talk of it but I don't think it ever happened.

I have seen a few Utube videos of a fellow winding up and flying his actuator planes very successfully.

Hope this helps.
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Phil_G
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Re: Escapement driver from PWM

Post by Phil_G » 05 Dec 2019, 09:21

Discussed here Scott:
viewtopic.php?f=62&t=93&p=177&hilit=pololu#p177
Cheaper to buy than to make but beware the 'slow-switching' ones

If you're using my S/C emulation encoder, it just plugs into rx channel 4

Cheers
Phil

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PaulJ
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Location: Ipswich, UK

Re: Escapement driver from PWM

Post by PaulJ » 05 Dec 2019, 10:25

Having "been there, done that and ticked the box", I can only echo what others have said...... By all means play with them on the bench but the bench is where these contraptions should stay! Escapements, and particularly OLD escapements are notoriously unreliable and have cost me several models and much loss of pride! Phil's system of a servo, driving a torque rod works beautifully! On the ground you can't tell the difference and in the air it works EVERY time and when you crash, at least you know it was your fault and not that wretched skipping escapement!.......
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"You know it makes sense"! :P

Paul

Scott Todd
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Re: Escapement driver from PWM

Post by Scott Todd » 05 Dec 2019, 15:02

I was told the same thing in the early 80's when I wanted to fly RC helicopters as a college student. And there are dozens more examples of me being told I couldn't or shouldn't do something Modeling related. It would be arrogant (which I most certainly am) to list them so I'll refrain.

I just want to fly an escapement. Just like I wanted to fly helicopters, blimps, RC Skydivers, Rocket Powered Shuttle stack without fins, FPV before it was FPV, and the list goes on. I don't need it to be on a well crafted delicate model. I tend to fly modern, reliable equipment on those. I plan on using a foam board airplane which I stated I could build in about an hour and provided details and a photo. I also stated how I would have modern redundancy for safety.

I worked my way thru Engineering School working in hobby shops. I have been sponsored by several major brands and owned my own shop for 8 years before selling it. It has always bothered me a little when I hear modelers discouraged. I always want to encourage people to follow their dreams. Sometimes that encouragement comes with recommendations of more training, research or help. But I always try to encourage rather than discourage.

Thank you Phil for the recommendation . That's exactly what I was looking for.

Tobe
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Location: Varberg or Stockholm, Sweden

Re: Escapement driver from PWM

Post by Tobe » 05 Dec 2019, 16:29

If all concerns are taken I don't see why you shouldn't. Pete Christy and a few others flew escarpment at Ponte last years successfully.
It's more an issue of responsibility to do it with the right approach safety minded.
I sure think...if...go for it.

Cheers

Tobe

Martin
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Re: Escapement driver from PWM

Post by Martin » 05 Dec 2019, 17:43

I suppose we could design and 3D print some modern escapements. The coils and armatures could be taken from modern relays. And (if that's what people want) we could add an automatic winder to keep the rubber band (or spring) wound by an electric motor so there was no danger of losing control because the rubber band didn't have enough turns.

The whole thing would be heavier than a modern servo with the same power, and probably not as reliable either - but it might be more reliable than a real vintage escapement.

There doesn't have to be a "good reason" for it - the hobby is all about fun. Providing we're not being reckless then we should be okay - and with a lightweight plane and some sort of modern reliable throttle control, then I think it would still be safer than some of the heavier and faster models we fly.

belli
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Joined: 19 Feb 2018, 19:19

Re: Escapement driver from PWM

Post by belli » 05 Dec 2019, 18:29

You've got some good ideas there Martin, it certainly has got my grey matter ticking...

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