EEVblog Electronics Community Forum
EEVblog => EEVblog Specific => Topic started by: EEVblog on January 20, 2015, 11:37:47 pm
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Dave tears down a top quality industrial joystick, the Penny + Giles JC6000 rugged joystick controller.
Thanks to http://www.controldevices.net/ (http://www.controldevices.net/)
EEVblog #706 - Joystick Porn (https://www.youtube.com/watch?v=MCDsge-3z0U#ws)
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About the symmetrical comment: digging from my memory from the time I worked in an automotive company - back in the 80's:
To achieve ISO-90XXX certifications, you have to have a single way to assemble something.
You can choose to explain the correct way in documentation (but then that documentation has to be available on the work floor), or design the parts in a way that they can only be mounted in one way.
If the certification inspector visits the work floor, she 'll typically ask: 'can I mount it the other way around?'
If you say 'yes': that's a minus point. They start challenging the consistency of your processes.
If you say 'yes, but the doco says that it should be mounted in a particular way': that's good.
If it can only be mounted one way: no questions asked.
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Just puzzled to see, that there is a mechanical wiper. :o
I've repaired some electric wheelchairs, and interesting to note, joysticks used in them does not contain any movable machanical parts, rubbing each other (except the movable stick of course). The sensing was done via inductive coupling somehow. I haven't reverse engineered the joysticks, but I remember 4 coils there, and some simple electronic circuit made of jellybean parts like quad opamp (TLC274 actually) or 4000 series CMOS (4053). It was powered from 5V only and had two differential outputs, each proportional to the tilt of the stick in each axis.
I suspect, this "inductive coupling sensing" must be at least order of magnitude more reliable, than any scratchy wiper.
For those interested, some circuitboards had a label "Made in New Zeland", so hi there!
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Pronounced penny and Giles that rhymes with " tiles " Dave !
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Why would a garbage truck need a 360 deg joystick? You Aussies are weird. :)
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Pronounced penny and Giles that rhymes with " tiles " Dave !
It sounds like one of those husband and wife teams, but Penny and Giles were actually surnames.
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Why would a garbage truck need a 360 deg joystick? You Aussies are weird. :)
to the front of the truck, back of the truck (x axis)
closer to the kerb, closer to the truck (y axis)
perhaps? Just guessing!
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Dave, with that title I predict this video will break viewing records.
Does youtube release statistics on what percentage of viewers start a video but don't watch the whole thing?
There could be a lot of frustrated first time EEVblog viewers. :o
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Does youtube release statistics on what percentage of viewers start a video but don't watch the whole thing?
Yup. They call it "Audience retention"
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Here's why a garbage truck needs a joystick:
https://www.youtube.com/watch?v=z591G_PlkbQ (https://www.youtube.com/watch?v=z591G_PlkbQ)
I don't recommend you watch more than a minute of this. The person who shot the video really, really likes garbage trucks in operation.
The truck's garbage can manipulator is multi-axis. The operator can rotate the arm into the truck and back out, extend the grabbing fork, move the arm forward or backward a bit with respect to the truck to line up with the can, and open/close the jaws. There's a video camera to show the arm's position relative to the can.
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Would be interesting to know exactly what material that gromet for the axis retention mechanism is, since it seems to be THE most stressed component in the system.
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The "dual output" part of the P&G spec referrers to the position sensing method not the actual device output. By using two separate position measurement systems, position validation and sensing accuracy can be assessed by the internal micro, before a validated position request is sent out to the host system. The 3 switch upper pcb tracks give a hard, digital state for "left, "centre" and "right" and can be used as safety gate signals for the proportional signal. They can also be used to calibrate / adapt the proportional output, by recording the proportional signal at the point the digital one changes state etc.
A lot of automotive position sensing has gone to contactless measurement, using actively driven, inductive or capacitively coupled resolver type arrangements. These are obviously more robust without mechanical wear, but bring a higher development cost and circuit cost (although the cost of "single chip" resolver driver/measurement solutions has fallen massively)
Tier1s like Hella have developed a range of contactless position sensing tech for just this sort of application:
(http://www.kfztech.de/kfztechnik/elo/sensoren/dkp/cipos.jpg)
(http://cdn.autocentre.ua/ac/09/07/images/12/Tech-p0000417.jpg)
http://www.hella.com/microsite-electronics/assets/media/06_CIPOS_gb_druck.pdf (http://www.hella.com/microsite-electronics/assets/media/06_CIPOS_gb_druck.pdf)
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There are numerous contactless sensing methods today. Very precise one is also magnetic / hall sensor. And I think almost every mil. grade potentiometer-like sensor uses wirewound resistor, not carbon layer on a PCB.
I just wonder, why did they used a single scraper wiper potentiometer. I've noticed, they have there only single touchpoint wiper. Almost any good potenctiometer, even those chinese cheap ones (16mm carbon, spline shaft), use multi-point wipers. In those chinese pots, there are typically 3 or 4 small wipers in parallel, to retain good electrical contact.
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I just wonder, why did they used a single scraper wiper potentiometer. I've noticed, they have there only single touchpoint wiper. Almost any good potenctiometer, even those chinese cheap ones (16mm carbon, spline shaft), use multi-point wipers. In those chinese pots, there are typically 3 or 4 small wipers in parallel, to retain good electrical contact.
The wiper consists of many small wires connected in parallel. If you watch closely you can see only a part of the wiper bending when Dave touches it. In 1080p you can even see individual wires.
I have seen similar contacts used in gas pedals: It had one potentiometer for the actual throttle and a couple of contacts for idle and full throttle: If any of those contacts did not match the potentiometer output, the engine control unit went into fail save mode.
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OK, my fault, I will watch again, look more closely.
But still I think the carbon scraping sensor is the least reliable and cheapest (to make the sensor element itself), compared to any other (inductive coupling, capacitance, magnetic). Please correct me, if I am wrong. :-//
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I hope you put that joystick back in the truck, or I think recycling day will be interesting!
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I don't know about the Penny & Giles joystick that Dave has but the ones they make for wheel chairs are certainly no joy. My wife has to use a power chair after an accident some years ago, the last two chairs she had got through 7 replacement or repaired joy stick units in 5 years between two chairs. The chair she has now chosen due to the power electronics being separate from the joy-stick unlike the previous chars which had a combined unit has had to have the joystick repaired 3 times in 20 months all due to the case splitting, the previous units it was always the control bridge that broke, so frequently that we purchased a spare control unit.
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Here's why a garbage truck needs a joystick:
https://www.youtube.com/watch?v=z591G_PlkbQ (https://www.youtube.com/watch?v=z591G_PlkbQ)
I don't recommend you watch more than a minute of this. The person who shot the video really, really likes garbage trucks in operation.
The truck's garbage can manipulator is multi-axis. The operator can rotate the arm into the truck and back out, extend the grabbing fork, move the arm forward or backward a bit with respect to the truck to line up with the can, and open/close the jaws. There's a video camera to show the arm's position relative to the can.
I've always hated how most gaming joysticks are too easy to push diagonally unless you're really paying attention.
Were I live the trucks aren't that fancy and only the compostables go in one of those wheeled bins which get attached to the lifting mechanism by hand so the machine only needs a simple lever. The problem with them is that the stuff freezes to the bottom of the bin and sometimes they get placed back on the ground too hard and the frozen plastic cracks.
I guess that's not a problem in Australia :)
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Here in S Africa it is a rear filling plate compactor or rotopress ( or if you are Veolia it is an old front loader) with a driver and 2 loaders, and another 2 who go before and after to pick the bins into the street ( a lot are locked up, otherwise they disappear as convenient scrap carriers) and deposit them back to the locations afterwards.
Have had the one truck where a wheelie bin got stuck after it fell off the lift into the back, and they simply crushed it, and carried on. The same truck had an issue last year where the load caught fire and burnt inside the compactor, they just dumped a fire extinguisher into the back and drove to the dumpsite.
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Stronger joystick feedback in diagonal direction is useful when operations joystick controls in X/Y axes are largely independent. This includes X/Y tables/mills/lathes/CNC/cranes/garbage trucks/etc., also aeroplanes (because roll is very different from pitch). You usually want to adjust only one axis independently - thus diagonal restriction has massive advantage.
However, when controls in X/Y axes are not that independent, diagonal restriction makes no sense. This includes most helicopters (where constant adjustment is required in all directions).
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Just puzzled to see, that there is a mechanical wiper. :o
Remember that those joysticks will be sold as components for a multitude of different industrial machines.
The interfaces provided by such industrial machine designs can be different, depending on the age of the design, operational requirements and perhaps even dependent on matters related to certifications or patents.
Many modern machines with digital control systems will likely offer some digital bus, in which case the joystick would likely use digital hall-effect, optical or similar sensors. On a related note: watch the label on the second joystick at the end of Dave's video. It says "Sample with CO hall switches". If i am not mistaken, CO stands for "CANbus output".
There might be reasons to choose other sensor types over (digital) hall-effect sensors in machines which produce or are exposed to stray magnetic fields (those could affect the hall sensors of the joystick and produce undesired signal noise or drift). But this begs the question of why using potentiometers instead of optical sensors in cases where hall-effect sensors are not feasible. The only reason i can think of for offering potentiometer sensors is to ensure compatibility with a base of older existing machine designs which only provide analog interfaces that tap the potentiometers directly.
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Pronounced penny and Giles that rhymes with " tiles " Dave !
Penny and Giles are well known in the UK for their faders in high quality audio mixing desks.
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Good quality wipers and ceramic resistor material should do well over a million cycles of operation in the joystick, and with the 2 separate contact systems you can see there is a built in deadband in the middle to compensate, with the lower contact set simply doing a mid, up/down and full scale digital position, and with a centre tapped carbon track to make a reliable mid position voltage as well. Likely the controller provides a voltage output that is not the actual contact voltage, but a smoothed, filtered and denoised output that tracks the input faithfully but which does not jump even as the track ages.
Likely there it is a digital bus, but the data is the same. You probably have the mid position having no response till it is moved out a bit, then it has a fine position till mid range then the steps are larger till full scale near the outside. Buttons are nice with hall sensors and they probably will outlast the joystick. Having a reliable push switch is hard, and those are nice, and probably a lot cheaper than using the fully specced aerospace contact versions, which likely would not fit as they are generally deeper behind the panel. As they only do TTL level switching it is a good use, as the ones I am thinking of are rated for 115VAC400Hz/28VDC 2A use.
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Couldn't tell by the video, but was the 2nd stick hall effect based? looked like a different construction that the unpopulated one.
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Both use a carbon pot and a wiper. Hall switching is not easy if you want a linear output that is stable without any periodic recalibration. The sensors tend to drift with time and temperature, and getting a magnetic field that is linear in a small area is hard to do easily, and the magnet will need to be calibrated, as well along with being very sensitive to stray fields, which is very likely in an industrial control panel where you might have tens of amps of current flowing right next to the sensor. You can use multiple hall sensors but then the design becomes more complex very fast and linearity becomes harder to achieve. A pot is linear and easy to drive, and can easily be made to last the cycle life required with only a thin contact lube applied during assembly.
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On the video while looking at the products they offered, they do have optional hall effect based sticks, not just the buttons but I think it implied the actual axis.
FWIW Xbox One controllers use hall effect for their analog triggers.
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I work for a large global industrial lift truck manufacture. (A fork lift)
Some of our class 1 and class 2 stand up warehouse product trucks use a very similar in design joy stick.
Over the years we have used many different designs. These things are very fascinating since you are able to control all functions of the lift truck with one hand. Travel; raise lower forks, tilt, side shift, ect.
That’s about all I am allowed to say.
Nice video Dave.
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Those joysticks are only industrial grade definitely not military specification.
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Those joysticks are only industrial grade definitely not military specification.
??
'Industrial' can be better than 'mil-spec'. Industry can spend whatever the hell it wants to. Mil-spec always goes through a lowest-bidder process and usually has a budget limit.
Also: Mil-spec can be old. eg. The M16 rifle was designed in the 1970s and hasn't changed much even though we have much better metals and manufacturing processes. You can get a much better M16 now than the mil-spec variant.
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Also: Mil-spec can be old. eg. The M16 rifle was designed in the 1970s and hasn't changed much even though we have much better metals and manufacturing processes. You can get a much better M16 now than the mil-spec variant.
You can even get ones which don't shit all over their insides!