On 30/07/2023 10:55, Chris Green wrote:

Jan Panteltje <alien@comet.invalid> wrote:

On a sunny day (Sat, 29 Jul 2023 19:27:46 +0100) it happened Chris Green
<cl@isbd.net> wrote in <2a2gpj-7p752.ln1@esprimo.zbmc.eu>:

Theo <theom+news@chiark.greenend.org.uk> wrote:

Ahem A Rivet's Shot <steveo@eircom.net> wrote:

On Sat, 29 Jul 2023 12:08:27 +0100
Chris Green <cl@isbd.net> wrote:

No, sadly those E-Ink displays are too slow. I don't need really fast >>>>>> refresh but I do need to be able to refresh in, say, 100mS (or maybe a >>>>>> bit more).

Do you need to refresh the whole screen? Many of the e-ink displays are >>>> able to do a partial refresh in much shorter time.

No, I don't need to refresh it all. The only relatively fast refresh
is for the rudder position indicator which would just be a single dark
cursor (or similar) moving about.

Am I missing something if I propose an old analog meter where the hand shows the rudder position?

No, it's an approach that I'm seriously considering. As the
'transducer' at the rudder end is simply a pot stuck on top of the
rudder post the whole thing can be analogue. I'm actually thinking
that an edgewise meter might be best.

If you decide to use e.g. a radio control servo, there are very
inexpensive 'servo testers' which do in fact have a pot in the middle.
The whole lot could be had for just a few dollars. You could wire your
pot up to them. Or generate your own PWM with a pi - the servo spec is a
20 Hz (or thereabouts) repetition of a 1-2ms pulse, with 1.5ms being the putative 'straight ahead' position.


And every time the servos dies its trivial money these days to plug in a
new one

Analogue meters don't come cheap or with suitable scales these days. And
thay are soewahtt fragile.


--
When plunder becomes a way of life for a group of men in a society, over
the course of time they create for themselves a legal system that
authorizes it and a moral code that glorifies it.

Frédéric Bastiat

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On a sunny day (Mon, 31 Jul 2023 10:38:29 +0100) it happened The Natural Philosopher <tnp@invalid.invalid> wrote in <ua7vem$388st$1@dont-email.me>:

On 30/07/2023 10:55, Chris Green wrote:

Jan Panteltje <alien@comet.invalid> wrote:

On a sunny day (Sat, 29 Jul 2023 19:27:46 +0100) it happened Chris Green >>> <cl@isbd.net> wrote in <2a2gpj-7p752.ln1@esprimo.zbmc.eu>:

Theo <theom+news@chiark.greenend.org.uk> wrote:

Ahem A Rivet's Shot <steveo@eircom.net> wrote:

On Sat, 29 Jul 2023 12:08:27 +0100
Chris Green <cl@isbd.net> wrote:

No, sadly those E-Ink displays are too slow. I don't need really fast >>>>>>> refresh but I do need to be able to refresh in, say, 100mS (or maybe a >>>>>>> bit more).

Do you need to refresh the whole screen? Many of the e-ink displays are >>>>> able to do a partial refresh in much shorter time.

No, I don't need to refresh it all. The only relatively fast refresh
is for the rudder position indicator which would just be a single dark >>>> cursor (or similar) moving about.

Am I missing something if I propose an old analog meter where the hand shows the rudder position?

No, it's an approach that I'm seriously considering. As the
'transducer' at the rudder end is simply a pot stuck on top of the
rudder post the whole thing can be analogue. I'm actually thinking
that an edgewise meter might be best.

If you decide to use e.g. a radio control servo, there are very
inexpensive 'servo testers' which do in fact have a pot in the middle.
The whole lot could be had for just a few dollars. You could wire your
pot up to them. Or generate your own PWM with a pi - the servo spec is a
20 Hz (or thereabouts) repetition of a 1-2ms pulse, with 1.5ms being the >putative 'straight ahead' position.

And every time the servos dies its trivial money these days to plug in a
new one

Analogue meters don't come cheap or with suitable scales these days. And
thay are soewahtt fragile.

I still have some nice big analog one...
Those servos are indeed cool,
http://panteltje.nl/pub/spare_servo_img_1559.jpg
http://panteltje.nl/panteltje/raspberry_pi_satellite_tracker/
I have played with those servos a lot:
http://panteltje.nl/pub/horizontal_IR_target_tracking_4686.avi
for all sort of things
Use a Raspberry Pi to control a Microchip 18F14K22 to drive a camera positioner...
https://panteltje.nl/panteltje/pic/camc_pic/
But some of my security cams already have x,y movement...
wrote some Linux code to control those too, if anyone wants it I can publish it.

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On 29/07/2023 10:18, The Natural Philosopher wrote:

But I have no idea how to drive it. What *is* an SPI? Ah! Serial
peripheral interface, so it wont be fast. e-ink is alway pretty sluggish though anyway.

It's not an old RS232 port! SPI is clocked up to 250MHz, and it's used
to drive many types of display on the Pi, including LCD and OLED, which
are much quicker that e-ink.

---druck

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On Mon, 31 Jul 2023 10:07:57 GMT, Jan Panteltje wrote:

If you decide to use e.g. a radio control servo, there are very
inexpensive 'servo testers' which do in fact have a pot in the middle.
The whole lot could be had for just a few dollars. You could wire your
pot up to them. Or generate your own PWM with a pi - the servo spec is a
20 Hz (or thereabouts) repetition of a 1-2ms pulse, with 1.5ms being the >>putative 'straight ahead' position.

If you want to use a servo to move a nice, big rudder position indicator, another low-cost option is to use a PICAXE device to drive the servo.

The PICAXE-08M2 is a simple, cheap 8-pin DIP package with a serial port
that's used both to load programs, which are written in a simple integer compiled BASIC, and to accept ASCII strings containing textual commands
and/or integer values. All PICAXE models have built-in firm-ware to drive
radio control servos. There are bigger chips, i.e. have more i/o pins, but those are likely to be overkill for this application.

The BASIC compiler/downloader can be run on an RPi, though you'll also
need a PICAXE USB Download Cable £14.99 inc. VAT, though most users only
need one of these: it connects to an RPi USB socket and has a 3.5mm coax
jack at the PICAXE end.

They also sell prototyping boards with a 3.5mm socket: an RPi, BASIC
compiler, prototyping board and download cable forms a fairly complete development and prototyping outfit.

Full details and prices are here: https://www.picaxestore.com/


--

Martin | martin at
Gregorie | gregorie dot org

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The Natural Philosopher <tnp@invalid.invalid> wrote:

Analogue meters don't come cheap or with suitable scales these days.

Unless you go to hamfests, in which case you can usually buy great
quality old ones for $5 or less. Ebay seems to have cheap Chinese
ones in the $5-$10 range too.

And thay are soewahtt fragile.

Well they _might_ not survive being dropped on the floor, but then
neither might a Raspberry Pi board.

--
__ __
#_ < |\| |< _#

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