Build a B&W film developing timer & twiddler - Cheap, Easy & it Works

[Niglyn]

Following on from my successful 'Build a shutter tester for focal plane shutters, cheap, easy & it works'

Here is my design of a timer for B&W film developing.

Many, like myself, use a stopwatch or a three line LCD timer, however, I thought it would be good to move into the 21st century with a colour screen & better functionality.

The developing timer allows the user to easily program the, initial & secondary agitations and interval, as well as stop & fix times, by turning a dial.

The screen then steps though each process, showing green when running, yellow to give a 10 second warning of an action to take place (agitation for example)
and then highlighted as the user has to carry out the action. Finished tasks then become grey. An audible cue will also be added.

Additionally, for twiddlers like myself, the timer drives a stepper motor to carry out all of the development agitation tasks & also stop & fix agitation if required. I will leave the debate as to whether to twiddle or not, to others.
Myself, I find it much easier to leave the developing tank in the water bath and twiddle. It maintains a better temperature, does not aerate the developer, stops water dripping & alleviates the threat of spillage during agitations.

The hardware is all cheaply available on Aliexpress & uses many of the same parts as the shutter tester. Where possible, I have kept the wiring identical.
Basic practical skills are required to build the timer. All of the required electronic modules are pre-built, so there is little or no soldering required, as push-fit or screw terminals are used for the connections.
Optionally, a li-po battery can be added, which is automatically charged & will power the timer in the event of a power failure.

Documentation is in the early stages and, along with the code, will be posted on Github, in the coming days.

In the meantime, thought it would be good idea to post some photo & get feedback or ideas for changes or additions.

Here are some (poor) photos of the screen during various stage of a development cycle.

Link to the shutter tester thread.

Build a shutter tester for Focal Plane shutters - Cheap, Easy & it Works

Just built the tester and I wanna say thank you for the detailed explanations. Here are my results for a Canon AV-1. As expected, there are a lot of inconsistencies at higher shutter speeds. Am I reading the results correctly by saying that the first curtain is slowing down/ second curtain is...

www.photrio.com

 

[albada]

This is probably the most sophisticated developing timer in the world. I'm still using a wind-up mechanical timer.
May I ask for the make, model#, and hopefully a link of the display?

 

[mshchem]

Yeah, I use a Gra Lab timer. Or my wrist watch or my phone. Etc.

 

[Niglyn]

Hi, Yes, I have just used a cheap stopwatch in the past. Works fine, but one has to stand there watching it, rather than getting on with other important tasks, like making tea )


The screen is a 4 inch colour TFT display. It is the single most expensive part at £7.62. (ensure the correct item is selected from the little icons). I chose this one , as whilst a little more expensive than the 3.5" screens, I find the larger screen easier to see.

https://www.aliexpress.com/item/1005003033828159.html?spm=a2g0o.order_list.order_list_main.120.e3f31802EBPurI

Other parts are cheap, processor board is £1.37, for example.


A bit of time spent on Aliexpress, to get the combined & free (if total over £8) shipping, should get all the parts for under £20 (excluding optional auto-twiddling). I have done my best to detail the cheapest suppliers on Aliexpress & the ones that do combined & free shipping, where possible.
The parts list document has links for the parts.


Have put the initial documents on Github. It will allow eager beavers to order the parts. The caveat of course is that there maybe a few changes made, although my version using the parts specified is working fine.


User instructions, code will be added to Github as soon as I can get them done.


Would be great to hear more feedback &/or improvement suggestions, or indeed ideas for other projects.

 

[ic-racer]

Another nice project!

 

[chuckroast]

Here's my contribution to that cause - it adjusts running speed based on developer temperature so you don't have to look up time/temp curves:

tundra/devtimer

gitbucket.tundraware.com

 

[Niglyn]

Hi Chuck, had a look at your project. A neat idea. I assume the code refers to the spreadshet to select the correct data?


I did think about wi-fi onto the massive dev chart, (esp32 has wi-fi) so the user can import the development data, but then that becomes a faff, so might as well just use a laptop running a dev-timer app. All this takes one away from the idea of a dedicated timer.


I have the development timer sitting here, all working nicely. I'm just tinkering with it, changing things like 'Button 1' to say 'Yellow Button'
Nobody has asked for the code yet, so I'm assuming it will not be a popular project.


Parts list is already on Github & I have the schematic ready to upload.


I might do an enlarger timer next. The ones that work in stops are really expensive. Seem quite easy to input start time, e.g 4 seconds, then the timer will bang off 4 second exposures (or 2 second for half stops) to make a test strip. Then timer can work in stops (really good once one gets used to the idea) or old fashioned seconds. Output to a opto-coupled relay module to power the enlarger.

 

[chuckroast]

Hi Chuck, had a look at your project. A neat idea. I assume the code refers to the spreadshet to select the correct data?

The spreadsheet was used to explore and document different ways of determining temperature compensation factors, whether by formula or by looking up manufacturer's table data, and then comparing these different methods against each other to computer divergence/error.

However, the code actually embeds a static lookup table for the correction factors (based on the spreadsheet work, to be sure), one for paper, and another for film. It does not dynamically look this up in the spreadsheet.

I did think about wi-fi onto the massive dev chart, (esp32 has wi-fi) so the user can import the development data, but then that becomes a faff, so might as well just use a laptop running a dev-timer app. All this takes one away from the idea of a dedicated timer.

I am less impressed by the Massive Dev Chart because it's pretty inconsistent even within a given film/developer combo, and in many cases diverges from my own measurements as confirmed by a densitometer.

I have the development timer sitting here, all working nicely. I'm just tinkering with it, changing things like 'Button 1' to say 'Yellow Button'
Nobody has asked for the code yet, so I'm assuming it will not be a popular project.


Parts list is already on Github & I have the schematic ready to upload.

What is the gitbub URL? Is it public?

I might do an enlarger timer next. The ones that work in stops are really expensive. Seem quite easy to input start time, e.g 4 seconds, then the timer will bang off 4 second exposures (or 2 second for half stops) to make a test strip. Then timer can work in stops (really good once one gets used to the idea) or old fashioned seconds. Output to a opto-coupled relay module to power the enlarger.

I have also been thinking about building an enlarging timer. In my case, I have these requirements:

- Two timer settings so I can set one for soft light exposure and the other for hard light for split vc printing.

- 0-100% intensity adjust for each of the timers to handle dry down adjustment and other incremental tuning.

- Physical knobs to set time for each - I hate pushing buttons, it's slow and inefficient.

- Relay based activation because cold light heads produce a real wallop of an inductive kick.

- Ability to turn the display/LEDs waaaaaay down so they don't fog paper.

 

[Niglyn]

I have also been thinking about building an enlarging timer. In my case, I have these requirements:

- Two timer settings so I can set one for soft light exposure and the other for hard light for split vc printing.

Easy, maybe 2 or more memory functions to toggle different settings

- 0-100% intensity adjust for each of the timers to handle dry down adjustment and other incremental tuning.

Not sure what you mean here

- Physical knobs to set time for each - I hate pushing buttons, it's slow and inefficient.

Yes, I agree. I use a rotary encoder, with acceleration, so easy to dial in big changes or small steps

- Relay based activation because cold light heads produce a real wallop of an inductive kick.

Yep, good old fashioned relay. Cheap opto-isolated modules available. These can be mounted in a separate unit, incorporating a socket for the enlarger & lead to plug into the mains

- Ability to turn the display/LEDs waaaaaay down so they don't fog paper.

TFT screen has built in LED. Have never tried dimming it.


Anyway, here is the link to my github for the film develop timer. Stlll early days, with just basic information there at the moment. I have not put the code there, as I am still tinkering with it, but if someone builds the hardware bofore the first release. I'm happy to send them the beta versions to play with.

GitHub - billbill100/Build-a-B-W-Film-Developer-Timer-Auto-Twiddler-Cheap-Easy-it-Works: Build a Black & White Film Developing Timer with optional motor driven twiddler for agitation

Build a Black & White Film Developing Timer with optional motor driven twiddler for agitation - billbill100/Build-a-B-W-Film-Developer-Timer-Auto-Twiddler-Cheap-Easy-it-Works

github.com

 

[chuckroast]

Easy, maybe 2 or more memory functions to toggle different settings

Not sure what you mean here

Yes, I agree. I use a rotary encoder, with acceleration, so easy to dial in big changes or small steps

Yep, good old fashioned relay. Cheap opto-isolated modules available. These can be mounted in a separate unit, incorporating a socket for the enlarger & lead to plug into the mains

TFT screen has built in LED. Have never tried dimming it.


Anyway, here is the link to my github for the film develop timer. Stlll early days, with just basic information there at the moment. I have not put the code there, as I am still tinkering with it, but if someone builds the hardware bofore the first release. I'm happy to send them the beta versions to play with.

GitHub - billbill100/Build-a-B-W-Film-Developer-Timer-Auto-Twiddler-Cheap-Easy-it-Works: Build a Black & White Film Developing Timer with optional motor driven twiddler for agitation

Build a Black & White Film Developing Timer with optional motor driven twiddler for agitation - billbill100/Build-a-B-W-Film-Developer-Timer-Auto-Twiddler-Cheap-Easy-it-Works

github.com

What language did you code this in?

 

[Niglyn]

What language did you code this in?

Mainly gibberish and C++ )
When raw speed is needed, a bit of assembly.


I post the compiled Hex code, to flash directly to the processor.
As I use blocks of pre-written code (to save me having to write the same stuff over and over) and then call them as a library, it would end up too complex to publish the code directly.


I have the working code sitting here now, all working. Until somebody requests it, I will continue to a tinker and add functionality. It no auto-corrects input errors, so if the user dials down the dev time, for example, agitation time may longer than the dev time.


Also planning to add a memory function, so it remembers the settings at power off. Might also add multiple memories, so different setups can be saved & easily recalled.

 

[Niglyn]

Developing timer now in a project box.

Not the best, but with very limited tools, I don't think it is too bad.

Still waiting for two buttons to arrive, an Orange (could use blue from the button multipack, but don't want it confused with the encoder) and a red push on/push off for an e-stop for the auto-tiddler.

More documents uploaded to the github

billbill100 - Overview

billbill100 has 8 repositories available. Follow their code on GitHub.

github.com

 

[Niglyn]

V1.0 25/02/2024​

Developing Timer Operating Instructions​

The Developing Timer works in exactly the same way as if one were using a standard timer or stopwatch.

However, by setting some basic parameters, the Developing Timer will step though each stage of the develop/stop/fix process, audibly and visually alerting the user that another operation is shortly due, or is taking place.

In this way, the user does not have to constantly watch the timer or have to remember when to stop developing or when and how long each agitation should be etc.

The Develop Timer is a modern take on the basic three-line LCD developing timers one can purchase, with dev/stop/fix times. Now using a modern colour display, easy time input with both visual & audible prompts & warnings.

It has been designed to be easy to use. Just press one knob to select the different times and turn the same knob to change them.

It is presumed the standard method of development timings are used. Developer is poured in and then the timer started. 10 seconds before end of development, the developer is poured out, with the Stop bath being poured in exactly at the end of development time.

To set the times:
Pressing the Blue knob once will place a red mark next to the Develop Time.
Turning the Blue knob will allow the developing time to be set. A maximum development time of 99 minutes 59 seconds can be set.

Pressing the Blue knob a second time, moves the red mark to the next line, Initial Agitate.
Turning the Blue knob will allow the Initial Agitation time to be set.

Pressing the Blue knob a third time, moves the red mark to the next line, Agitate Every.
Turning the Blue knob changes the interval between secondary agitations.

Pressing the Blue knob a fourth time, moves the red mark to the next line, Secondary Ag(itation) Time.
Turning the Blue knob changes the length of each secondary agitation.

Pressing the Blue knob a fifth time allows setting of the Stop bath time and a final press allows setting of the Fix bath time. A maximum time of 60 minutes can be set for these.

As an example, developing Ilford FP4 in ID11.
The developing time is set at 11 minutes.
Initial Agitation is 30 seconds
Secondary agitation is every 60 seconds (1 minute)
and each secondary agitation is performed for 10 seconds.

Note:- as with normal manual development, all timings are taken from development start. So initial agitation is from start of development time for 30 seconds. Secondary agitation interval (Agitate Every) is also taken from start of development time. So, in this example, agitations will take place exactly on the minute, for 10 seconds duration.





Stop bath has no programmable agitation times & it is usual for the stop bath to be continually agitated.
Visual prompt will be given, but there will be no audible warnings until 10 seconds before Fix Time ends.
Auto-Twiddle, if selected, will turn for the whole Stop Bath time.

Fix bath gives initial agitation of 10 seconds and further agitations on the minute, of 10 seconds. Audible and visual notifications are given.
Auto-Twiddle, if selected, will turn for 10 seconds every minute









To start the Developing Sequence.

Pour in the developer & Press the Green button.

Immediately, Develop Time will start counting down.
At the same time, the Initial Agitation time will start to countdown, highlighted in Yellow/Red, with a deep pitch audible alert and on-screen prompt, requesting the user to start agitating.
This will continue until the Initial Agitation time has counted down to zero.
In our example, this will be from 11.00 minutes to 10.30 minutes, i.e 30 seconds.

The Agitate Every timer will also be counting down and 10 seconds before secondary agitation is due to take place, the Develop Time will change colour to Yellow and a high pitch audible alert will be heard, to notify the user that an an action, soon required.
In our example this will start at 10.10 and end at 10.00

When Agitate Every timer has counted down to 0, the Secondary Ag(itation time) will be highlighted Red/Yellow, with a deep pitch audible alert and on-screen prompt, requesting the user to start agitating.
(in our example, this will start at 10.00 and end at 9.50)

The sequence of Agitate Every and Secondary Ag(itation time) will repeat for the length of the developing time. In our example, 10 seconds before each complete minute, the high pitch warning will be heard & on the minute, a deep tone will be heard, prompting the user to start agitating.

Note: No agitations will be performed within the final 20 seconds of development time.

20 seconds before Develop Time ends, Develop Time will be highlighted in Yellow and a high pitch auditable tone heard, to warn the user that an action will be required in 10 seconds.

10 seconds before Develop Time ends, the tone will change to a deep tone, with an on-screen prompt, instructing the user to pour out the developer, A tri-tone will be heard at end of development time.

The Stop bath should be poured in immediately at the end of the development time. In our example, 11 minutes.

This completes the Developer cycle and the timer will pause, with an on-screen prompt, waiting for user input.



The Stop Bath.

When the Stop bath has been poured in, press the Green button.

The Stop Time will now count down for the allotted time.

As the stop bath is a very short duration & is normally agitated for the whole duration, the Stop Time will be highlighted Yellow/Red for the whole countdown period, but there will be no audible agitation warning.

10 seconds before the end, a deep pitch audible alert will be heard. At the end of Stop Time, a tri-tone will be heard & an on-screen message to pour out stop bath & pour in Fix bath.

The Fix Bath.

When the Fix bath has been poured in, press the Green button.

The Fix Time assumes standard fixing of agitation for the first 10 seconds and 10 seconds every minute.

For the first 10 seconds, Fix Time will be highlighted Yellow/Red, on-screen prompt & a deep audible tone, alerting the user to agitate.

For 10 seconds every minute, the same warnings will be given, whilst Fix Time counts down to 0.
At the end of which, a tri-tone will be heard & the screen will prompt to wash film.

Pressing the Black button will reset the Developing Timer, ready for another developing cycle.

Auto-Twiddler.

If the optional stepper motor is installed, it works as follows.

Pour in the developer and press the Green button to start development, tap the tank to dislodge bubbles and place the Auto-Twiddle mechanism onto the developing tank.

To start auto-twiddling Press the Yellow button. The Auto-Twiddle icon will turn yellow & run for the duration of Initial Agitate time.

When secondary agitations are required, the motor will automatically start to turn.

The speed of auto-twiddling is adjusted by turning the Blue knob during Development. The RPM is shown on the display.

The auto twiddler can be turned off at any time by pressing the Yellow button. Auto-Twiddle will turn Grey on the screen and the motor (if running) will stop. Pressing Yellow againthe button will re-activate auto-twiddling.

At the end of development, the auto-twiddler turns itself off and the Yellow button must be pressed for auto-twiddling if required during the Stop Bath process.

Similarly, at the end of the Stop Bath process, the auto-twiddler turns itself off and the Yellow button must be pressed for auto-twiddling if required during the Fix Bath process.

The design & build of the auto-twiddler mechanism is left up to the user. It is noted that the cheap Chinese developing tanks also raise and lower the film holding spiral during twiddling, which is an upgrade to the standard Paterson rotation only. Jobo & its clones have no provision for twiddling.

Important Notes.
It is important that the film is orientated correctly into the developing tank if twiddling (manual or auto). The film should be wound clockwise, starting from centre to the outside, when looking from above. This way, when twiddling (clockwise), fresh stock will be pulled into the film leading edge and pushed though the film.



Film wound & loaded clockwise in developing tank, when viewed from above





General Notes.
Initial agitation time cannot be set longer than development time – 20 seconds.

Secondary agitations will not be performed in the final 20 seconds of development.

Secondary agitation will not start until at least 20s after initial agitation has finished.

If the E-stop button is pushed whist motor is running, the motor will stop dead, with no deceleration.

To save the current settings, press and hold the Black button, press the Green button and release both. The Developing Timer give a high pitch tone. This can only be performed when not in a developing cycle.

To Factory Rest to default parameters, press and hold the Black button, press the Yellow button and release both. The Developing Timer will blow a raspberry & reset. This can only be performed when not in a developing cycle.

The Black button may be pressed at the end of the development or stop cycle & it will reset the Development Timer back to the setup screen.

The debate as to agitate by inversion or twiddling will go on forever.
With Patterson tanks, one has the choice of either, whereas Jobo has no provision for twiddling & the Chinese tanks can only be twiddled and not inverted.

From my own experimentation, I have found twiddling every bit as good as inversion, with the added benefit that there is no chance of chemical leaks or the lid popping off whilst inverted. It also stops over aeration of the Developer, especially if only developing one film in a multi-film tank (Patterson themselves warn of over vigorous agitation in this situation)

When using a water bath, as I always do, to maintain an even temperature, one does not get water everywhere during the agitations.

The water bath, I use for the rinse, as it is at the correct temperature, using the method Patterson describe. Auto-twiddling ensures that no errant chemical has found its way into the water bath.

billbill100 - Overview

billbill100 has 8 repositories available. Follow their code on GitHub.

github.com

 

[albada]

I have also been thinking about building an enlarging timer. In my case, I have these requirements:

- Two timer settings so I can set one for soft light exposure and the other for hard light for split vc printing.
- 0-100% intensity adjust for each of the timers to handle dry down adjustment and other incremental tuning.
- Physical knobs to set time for each - I hate pushing buttons, it's slow and inefficient.
- Relay based activation because cold light heads produce a real wallop of an inductive kick.
- Ability to turn the display/LEDs waaaaaay down so they don't fog paper.

Be sure to put an appropriate capacitor across the relay to absorb the inductive flyback. Otherwise, sparking will eventually destroy the relay's contacts. That's why old cars had condensers across their points.
I built two controllers for my LED-based enlarger, and am thinking of building a third smarter one. Based on my experience, I suggest:

• Use a 3.5- or 4.0-inch OLED or TFT LCD display. Another approach is a 4x20 character LCD with red backlight.
• For TFT, be sure it has the IPS feature (usually in the title of the ad). IPS provides a wide angle-of-view out to 80 degrees off vertical.
• Put two knobs on the left side of the display, and two on the right (four knobs total). Or three knobs on each side. This lets you change 4 (or 6) settings without pushing a button.
• Add a few buttons for things like B&W-split, B&W-nonsplit, color, dodge, burn, settings, start, cancel.

The display-surrounded-by-knobs design lets you try various display-layouts and features without changing your hardware.
Here's the format of the main B&W display I'm thinking of using:

Turning one knob will change time, grade, brightness (of the LEDs), or paper-type. No button-pushing.

Mark

 

[GBS]

Hi, really into this project. Thank you for sharing! I downloaded the Git, but I don't see any instructions for housing the stepper motor or how to connect it to the dev tank. Sorry, am I missing something? Thanks!

 

[Niglyn]

Hi,
Thanks for your interest in the project.
The Developing Timer includes the stepper driver, but it is up to the builder if they want auto-twiddling, to design the stepper-to-tank part themselves.

As I no longer have a workshop and almost no tools (but plenty of time to write code), I have not been able to construct a suitable interface myself. I would love to do this & experiment with different designs, but alas it is not possible.

The Rolls Royce solution would be a 3d printed lid with little teeth to engage with the teeth on the top of the Patterson System 4 tank. The stepper then mounts to the lid, pointing straight down & connects to a twiddling stick via a universal joint.

I am sure there are other ways to do this, even cutting a disc of wood or plastic & attaching a few teeth.
The important thing is to ensure the reels rotate and not the stepper.

I prefer twiddling to inversions. As I use a water bath, it saves water going everywhere & also less possibility of chemical leakage from the tank. The water bath, I then use to wash the film, so do not want any contamination from dripped chemicals in it.

When using a water bath, it is important to ensure the tank, or chemical bottles do not start bobbing about, when putting in/taking out chemical bottles.

Please keep us updated.

 

[GBS]

Hi,

Thanks for following up. This makes sense. I love your timer so I was hoping to figure out a lid solution. I don’t know CAD but I wish I did. I’ve tried a few times but have to dedicate my time to other things currently.

Someone else made an auto agitator lid, but the timer is less advanced than yours, but my friend built one and said it works well:

Automated Film Developing Tank

Automated Film Developing Tank: I recently got back to film photography after 20 years, and discovered that gone are the days of dropping off your film at the local drugstore. What to do?There were places for film developing online, but I was not keen on paying postage both ways. …

www.instructables.com

 

[bernard_L]

From my own experimentation, I have found twiddling every bit as good as inversion,

Did you include in your own experimentation the following experiment or equivalent:

1. One frame with the upper half heavily exposed and lower half barely exposed; upper/lower referring to the film situation in the developing tank;
2. Next frame uniform exposure; say, uniform wall, as per light meter, strongly de-focused;
3. Repeat for 5 frames, alternating
4. Develop with twiddler agitation
5. Digitize and boost contrast to make any lack of uniformity more easy to detect

I made that experiment once by accident. Not going to repeat. Or to risk repeating.

 

[bernard_L]

Be sure to put an appropriate capacitor across the relay to absorb the inductive flyback.

Be aware that even when the relay is OFF,there will be some AC on the output, flowing through the capacitor.
Quoting from: https://forum.allaboutcircuits.com/threads/calculating-values-for-an-rc-snubber.150655/

So I reasoned, "gee, if I use a much larger capacitor for the snubber then lots more noise will be inhibited, right?" ... and yes, I was right ... but the large cap allowed for so much current to flow through the arrangement that the motor started spinning without the fets being active!

A commonly used layout comprises a series combination of capacitor and resistor, called a snubber. Typical values seem to be 0.1µF and 100 ohms. See e.g. https://toshiba.semicon-storage.com/eu/semiconductor/knowledge/faq/opto/opto-059.html
(a solid state relay, but same issues) Note they also have a Gmov/varistor voltage limiter in parallel.

 

[RalphLambrecht]

Mainly gibberish and C++ )
When raw speed is needed, a bit of assembly.


I post the compiled Hex code, to flash directly to the processor.
As I use blocks of pre-written code (to save me having to write the same stuff over and over) and then call them as a library, it would end up too complex to publish the code directly.


I have the working code sitting here now, all working. Until somebody requests it, I will continue to a tinker and add functionality. It no auto-corrects input errors, so if the user dials down the dev time, for example, agitation time may longer than the dev time.


Also planning to add a memory function, so it remembers the settings at power off. Might also add multiple memories, so different setups can be saved & easily recalled.

consider selling it fully assembled and working for the not so handy darkroom workers.

 

[Niglyn]

HI,

If you have a mate with a 3d printer, you can use the stirrer_bottom_plate.stl here.

Automated Film Developing Tank

Automated Film Developing Tank: I recently got back to film photography after 20 years, and discovered that gone are the days of dropping off your film at the local drugstore. What to do?There were places for film developing online, but I was not keen on paying postage both ways. …

www.instructables.com

Also a locator plate and drive adaptor.

Also on that link are details to make one from wood.
(You do not need the sleeve or top plate)

If you are handy with a router, cut a circle a bit bigger than the diameter of the lid. Then rebate a grove, the diameter of the lid.
Just lining the grove with rubber may create enough friction, if not would be easy enough to cut a couple of slots and glue in a few teeth. Would only need 2 or four teeth.

If no router, cut a wooden circle by hand/jigsaw. Mark the tank top diameter on it & glue four small bits of wood just outside the drawn circle at 12, 3, 6, 9 o'clock.. This will keep the disc correctly located. either add rubber for friction or add some teeth to fit in the tank teeth.

All very easy to do with a few tools.

 

[Niglyn]

Here is a photo of the (new) 3d printed Patterson Super 4 Tank Lid.
It incorporates mounting for the stepper motor & teeth on the underside, to engage with the serrations on the tank rim.

A new twiddling stick will be available soon (printing now) which will connect directly to the stepper motor drive shaft.
stl print files on Github & Instructables.


Without a 3d printer, it is quite simple to make something similar from a piece of ply or plastic.

 

[Radost]

Yeah, I use a Gra Lab timer. Or my wrist watch or my phone. Etc.

When I start loading developing the first thing is to leave my watch downstairs. Watches are dangerous things. Never happened to me but a friend was loading tanks with a watch…

 

[mshchem]

When I start loading developing the first thing is to leave my watch downstairs. Watches are dangerous things. Never happened to me but a friend was loading tanks with a watch…

You know "Twiddling your stick" is prohibited by law in many areas

 

[mshchem]

Here is a photo of the (new) 3d printed Patterson Super 4 Tank Lid.
It incorporates mounting for the stepper motor & teeth on the underside, to engage with the serrations on the tank rim.

A new twiddling stick will be available soon (printing now) which will connect directly to the stepper motor drive shaft.
stl print files on Github & Instructables.


Without a 3d printer, it is quite simple to make something similar from a piece of ply or plastic.

View attachment 369231

Very nice!