Help with Servo Current Limiter on Picaxe Autopilot from Snoopy's Robot Boat

Robin Lovelock

Senior Member
Hi Guys. I hope this posting and the links get through to you. Following sent to other forums & networks ...

Hi Guys. I've updated Snoopy's "Blog11" on http://www.gpss.co.uk/rbblog11.htm and this is not just those into Microtransat and Trans-Atlantic Robot Boats - which can benefit from wisdom of pensioners into radio controlled boats - perhaps after radio controlled aircraft and drones ;-) Pensioners often have wisdom on a wide range of subjects, including physical & mental health, A.I., electronics, warfare, welfare, and much more ;-)

Technical Guys: can anyone help on that "servo current limiter" in Blog11 ? :)

is a 1.75 hour video with the trails of photos shot between Friday 4th until Thursday 10th October 2024. The video starts with Robin's usual amusing introduction, shot on Thursday 10th and recent days, walking down their front drive at 22 Armitage Court in Sunninghill. Robin shows you Snoopy's Robot Boat in the front garden, on 24/7 Static Test, researching improving solar power. Not yet done. The boat should soon be ready for a Bray Lake Test, before a 2024 Atlantic Attempt. Photo trails show how, with the right help, they might get the house, back to what is was several decades ago. This, and earlier videos, have important detail for potential helpers in "property maintenance" ;-) They need plenty of experience and "common sense" ;-) After the photo trails, Robin wraps up with video shot in July 2023: prophetic words of James Lovelock about Global Warming, and Robin's suggestions about the DVLA. He still has not received his driving licence. Most guys would be annoyed, but Robin is often amused by incompetence - so long as it does not result in suffering, pain, or death. It has been very "inconvenient", with more load put on June, coping brilliantly with her health problems. With the right "nudge", June spoke to the same paramedic at Magnolia House and got an X-Ray on 9th October. Results may be available on 11th October. The DVLA letter on Friday 4th appears, but is dealt with more clearly on Robin's PRESS and DVLA pages ;-) Yes, as can be expected, from Robin's career, then hobby interests, there are plenty of examples of people, GPS Tracking, and technology being exploited. e.g. wildlife and people caught on CCTV; Sunninghill Comrades Club; Pub Lunches ;-) The automatic subtitles/captions were soon available, with translation into any language. Well Done Youtube Guys, whoever and wherever you are ! ;-) Footnote: Youtube used to give a choice of three images, for the "title picture" - and now just one. Often a good choice. You can do it yourself - and not an image bigger than 2 MB ! Not difficult with old Paint. Google and Youtube things change - fewer people to employ and pay ? Bring back people, simply aided by A.I. ! :)

That's the Youtube description above. Topics overlap, and I've known for years that my best advice on anything, including technical things and health, is often from my overlapping networks of friends, both local and far away overseas. My thoughts are with you, in these difficult times.

Closer to home, thanks to my small circle of Grumpy Old Men, providing good health advice to wife June - key member Snoopy's Team-Joker, from when the late John Sylvester got me started. This morning, I had to ring old friend Gary Carter, of http://www.carmech.co.uk because we needed help to know how to get to the car battery of June's Merc K555GPS seen in the video. June hadn't told me she had an MOT at 1400 today - or we might have been better prepared: all three of the "fast starters" were flat, as was the K555GPS battery, because the car had not been used for days. "Be Prepared" is an old saying taught to school boys ;-) Gary is also the guy who gave me the first of Snoopy's Robot Boats - all on the "Snoopy" page http://www.gpss.co.uk/autop.htm and many linked pages :)

Take Care
Robin Lovelock in Sunninghill
http://www.gpss.co.uk and www.gpshobby.info and http://www.nhscare.info
"Contact" page http://www.gpss.co.uk/contact.htm
 

Buzby

Senior Member
This is the circuit I use when I need to limit current ... https://www.homemade-circuits.com/universal-high-watt-led-current-limiter/

This LM317 circuit just needs a single resistor to set any current. ( My latest circuit was for a lawnmower charger that must not provide more than 500mA. The resistor was 2.5R 1W )

However, the LM317 does introduce a volt-drop, so it may be best to put the limiter prior to the servo supply regulator, not in the actual motor supply.

Another, simpler, solution could be a resettable PPTC fuse. I've not used these, so can't vouch for them myself, but they are widely used in modern circuits.
 

Robin Lovelock

Senior Member
Brilliant Buzby ! Thanks. I took a quick visit and saw that simple LM317 circuit ! :) Can see me ordering some of 'em tomorrow - nah today ! :)
Writing this coming up to 0100 Saturday, after getting back from our Sunninghill Comrades Club - left there about 0025 :) Taa Muchly :)
Robin
www.gpss.co.uk
 

Robin Lovelock

Senior Member
Hi Guys - particularly Buzby. I've been updating that "blog11" on www.gpss.co.uk/rbblog11.htm with progress, particularly on that LM317 based current limiter. You need to scroll down to the latest stuff near the end, with relevant pictures. LOTS of photos taken, of step-by-step work, but that will be a few days before I publish the "Mid October 2024" Photo trail video. However, in short, I now have LOTS of LM317, from the two batches that arrived yesterday: 48 + 10 = 58 and I've only used 2, so far. The first was a "lashup" that worked OK, with 5 ohm, into my "Servo Test Rig" autopilot, based on my old Picaxe 08M solution. 10 ohms and it tended to "twich". But it was only when I tried the more neatly built LM317, on a bit of veroboard, that I started tests on the boat system - based on the Picaxe 28X2. This just twitched, even when I lowered the resistance by using THREE 10 ohm resistors. This is all shown more clearly in that "Blog11" above. You will see that I was wondering if the problems were related to the servo drive
system, coming out of my Picaxe 28X2 based autopilot. I certainly do not want to change this - I'd rather do it "cleanly" with a module between the
28X2 and the servo. You will see that this raises that earlier problem: I have no spares for that Picaxe 28X2 Autopilot. I repeat: I'm happy to pay anyone to build and supply something that has been tested. But let's not get distracted: maybe someone can suggest a simple test with what I have here. Thanks Buzby - it was certainly easy to get those LM317 and an easy job to put together ;-)
Take Care
Robin
www.gpss.co.uk and Snoopy on www.gpss.co.uk/autop.htm
 
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