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Nov 27, 2021, 12:07 PM
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slowmatch's Avatar
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Micro FF Timer with Speed Control


This is my latest FF electric timer intended for roughly peanut-sized multi-engine scale on one cell Lipo.
It has adjustable speed control for more practical trimming and a push button start. Time is adjustable from 7-45 seconds.

It's capable of around 5A which equates to a couple of 8mm motors or four 6mms

Micro Free Flight Timer with Speed Control (0 min 44 sec)


It weighs 0.4g and measures 11mm x 13mm (1/2" long) so just a bit smaller than a micro SD card.
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Nov 27, 2021, 05:40 PM
B for Bruce
BMatthews's Avatar
Or one slightly bigger single.....

I also love the throttle control option.

Are there copies for sale? If so how much?
Nov 28, 2021, 07:04 AM
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slowmatch's Avatar
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Thanks Bruce. After many years of mucking about with various iterations of the Peterborough Timer which is full power only, the throttle control was something of a holy grail

I really only made this for my own amusement since they take nearly a whole day to build. If there's some interest I might produce a few for sale but I have no idea what they are worth really. Less than my time to be honest! A production version would have to be a few mil larger to simplify and speed up the build.

Jon
Nov 28, 2021, 10:04 AM
Balsa Flies Better!
I don't want to take away from your accomplishment as I think you've done something really neat-

but if you're interested in a poor man's approach to p-nut sized electric power- a capacitor may offer a bunch of advantages. You're not going to get quite as long a flight, although from my perspective- a flight time of ~1 minute is possible. But you can buy a foamie airplane with such a power system for under $10. No timers needed.

I've been really tempted to do a DH-2 or an Airacuda. Problem with the Airacuda is a lack of plans- have a p-nut scale DH-2 plan- might blow it up a bit to 15" or so.

Sam
Nov 28, 2021, 12:55 PM
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slowmatch's Avatar
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Hi Sam,

I've played around with supercaps in the past but never really enjoyed the constant decay power profile. I was involved with developing a regulator that does permit a controlled constant output with a supercap but I've tended to concentrate on lipo and timers. I agree - caps definitely have their place, especially their simplicity. But I would say that lipo just about edges it for energy density and performance over all and once I've done the timer build and install then operation is very simple. Turn up and press the button

Jon


This is a simpler timer but you get the idea:

DC-5 Nearly OOS :) (0 min 53 sec)
Nov 28, 2021, 01:02 PM
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slowmatch's Avatar
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This is the supercap regulator circuit in action. It has some limitations but again - the ability to set the 'throttle' is very handy for trimming.

Using a Volt Regulator to Control a Supercapacitor for Free Flight (2 min 3 sec)
Nov 28, 2021, 04:30 PM
B for Bruce
BMatthews's Avatar
I had assumed that there would be a small micro controller in this to provide the PWM throttle effect and run the timer. But it looks like you might be doing this with hardware. Is that the case? Or is one of those packages a reduced pin package controller?
Nov 28, 2021, 05:01 PM
Balsa Flies Better!
Hi Jon

I understand where you're coming from and I watched the video of the DC-5 which really climbed out! However, I have a different perspective.

I fly a lot of rubber powered FF- and so the power burst and long cruise of a capacitor isn't irksome to me- it's actually a pretty good match for a rubber motor. What I like about the capacitor is the lack of worries and longevity. Nicads leak over time, lipolys have charging/fire issues and need to be disconnected to charge. The supercap is simple, rugged, and should have excellent longevity.

I certainly agree that lithium polymer batteries have much higher energy density and probably pretty comparable power density- which was supposed to be the forte of the supercap. But the rapid charge time of the supercap and the lack of a timer make this power source very attractive to me. If I want to power an airplane with a lipoly battery, odds are I wouldn't bother with a timer- radios are cheap enough. Note however, I still haven't built anything yet.

Sam
Nov 28, 2021, 05:32 PM
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slowmatch's Avatar
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Hey Sam, that's cool. I fly mostly rubber FF too but I just enjoy tinkering with electronics and seeing what I can be done - especially for the small multi-engine subjects that won't suit rubber.

Bruce, no it's not a micro controller although that could probably be smaller still. I am interested in learning to code but one rabbit hole at a time eh...(!) This circuit is basically two elements: stage one is an Op Amp Comparator set up as a one-shot monostable. This drives the Enable pin of stage two - a small package 555 timer set up as an astable oscillator producing PWM (Pulse Width Modulation)

It's a loooong way from a Peterborough Timer but you can still see it's genes if you look hard enough
Nov 28, 2021, 09:00 PM
B for Bruce
BMatthews's Avatar
Quote:
.......one rabbit hole at a time eh...(!).....
Wise words... wise words indeed.... We can often be our own worst enemies, eh?

What you describe is similar to the brushed motor RC ESC that a buddy and I built a few of during the old brushed motor times. One 555 section makes a triangle wave and the incoming pulse is "leveled" by an RC combo and a voltage comparator sets the PWM based on where on the triangle wave the comparator switches. It was a popular circuit from some magazine or other back in the day.
Nov 29, 2021, 05:35 AM
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Quote:
Originally Posted by BMatthews
What you describe is similar to the brushed motor RC ESC that a buddy and I built a few of ...
Sounds cool Bruce.
Nov 29, 2021, 04:06 PM
B for Bruce
BMatthews's Avatar
It was cool! .... back when the other option was a high current toggle switch flicked by a servo....
Dec 28, 2021, 08:53 AM
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domll's Avatar
Quote:
Originally Posted by slowmatch
Hi Sam,

I've played around with supercaps in the past but never really enjoyed the constant decay power profile. I was involved with developing a regulator that does permit a controlled constant output with a supercap but I've tended to concentrate on lipo and timers. I agree - caps definitely have their place, especially their simplicity. But I would say that lipo just about edges it for energy density and performance over all and once I've done the timer build and install then operation is very simple. Turn up and press the button

Jon


This is a simpler timer but you get the idea:

https://www.youtube.com/watch?v=YYVJlxg85yk

Did you get the model back
Dec 28, 2021, 11:50 AM
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slowmatch's Avatar
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Yes! It landed about three feet from the hedge - after getting to several hundred feet altitude
Dec 28, 2021, 03:40 PM
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That's very light! I guess four 6mm motors woukd be enpugh for a,peanut Barling Bomber. They make 4 mm motors, don't they? I suppose a Do X or a Ca-60 would require something a bit larger anyway. Plus, of course, about 100 times the patience I have. With 50 times my patience, a peanut Spruce Goose might be possible.

My own personal interest would be a reverse Peterborough timer to power a DT mechanism on a glider.

If I had an electric model, I might want reverse or a slow "idle" for DT purposes. Not sure if the motor would,burn out, though, if it got jammed when it came down.

How many parts and solder joints in your design?


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