Build the Robo-Box! 

You're welcome! It's your call, but I'd be a bit hesitant about reversing the rotation every 30 seconds as I think the Lab-Box is designed for one-way rotation: if you look at the 35mm reel ends in particular, you'll see they've got agitation "paddles" around the outside, and if you reverse the direction there's a risk of splashing chemicals back up into the loading compartment and cutter blade. (Ask me how I know this 🙀) On the other hand, it might be a really worthwhile improvement to use the Arduino to pause the motor occasionally at random intervals, to help break up flow patterns that otherwise might cause developing streaks -- as shown in the video, I give the tank a sideways shake occasionally to do this, but having completely hands-off operation would be nice! If you complete this build, be sure to post up and let us know how it works! One more point about agitation: If you're using partial fill (300ml) as I do, you're already doing a form of intermittent agitation. The point of intermittent agitation (regardless of the type of tank) is that while the film is static, the developer immediately adjacent to the film surface performs development and then becomes depleted by chemical action; when you agitate, fresh developer is brought into contact with the film, and this depletion/replenishment cycle helps provide a compensating effect. In the Lab-box, the time the film is at the top of the reel corresponds to the static part of the cycle -- the thin coating of developer clinging to the film becomes depleted, and then is replaced when the reel rotates the film back down into the developer. Since you're already getting intermittent agitation just by this cycle, there may not be any benefit in reversing the reel... other than reducing the risk of flow marks, which also could be done just by stopping the reel for a moment occasionally. Anyway, be sure to let us know how this works out!

@@jlwilliams wow. What a thorough reply. Thank you. Your points are all very valid and the random pausing is very interesting. I could also reverse the motor for only, say, 90 degrees and then brake it and head forward once more. I can also reverse the motor very slowly as I’ve discovered that using the arduino motor shield Rev 3 I can alter the pulse width modulation and hence the effective voltage and also the direction. If you google ‘Controlling a DC Motor with Motor Shield Rev3’ you’ll see the very essence of what I’m thinking. I bought the lab box on the kickstarter project, but I develop a lot of film and very soon realised that it was impractical for the same reasons as you. Today I was clearing out some cupboards and found it. It’s really cold and miserable in the UK in January so I saw a project, then found this RU-vid video and now I’m fully onboard. I probably still won’t use the lab box as my mainline development tank but I love the journey and so you’ve really got me started. As for posting the project here, yes I certainly will but in essence it’s your mechanical design but with the motor controlled by software as seen in the document referenced in the Google search above. Thank you again. Wonderful.

@@jlwilliamsI typed a long response to this but RU-vid seems to have deleted both that response and the other message (which I expected to be deleted) where I gave the link to the arduino pdf re motor control. I give up.

@@jlwilliams but it was an appreciative response.

Thank you very much!

Thanks! I'll bet a drill would work, if you chucked a pulley into it and made some kind of base to hold it at the right distance from the box...

Let me know how you come out and if you think of any improvements! Thanks...

@@jlwilliams As you said, turning the knob into a pulley will help. I have a handle version and will try to drift off the handle exposing the 6mm shaft. If that's achievable I'll fix a hub & pulley. Information for you is that the Pro lid has a different slope profile. The center of the shaft now aligns further down the slope of the lid, so I'm not sure if how effective the brass collar solution will be at keeping the knob seated. More to follow :-)

Thanks! I try to avoid having quite as many disasters as my fellow Midwesterner Buster Keaton!

Hello - Yes, I am using an O-ring and pulley without teeth, and it works reliably. The tension in the O-ring also is what keeps the frame in place on top of the Lab-Box. When I started working on the design, I was worried about slippage too. My original thought was to use a toothed belt and pulley on the motor, and to have the teeth engage with the knurling on the Lab-Box knob. However, as you probably know, this type of belt doesn't work well unless it engages with the pulley teeth exactly. I carefully measured the pitch (spacing) of the knurling on the knob, and could not find a belt with a pitch that would match it. So, I moved on to the idea of using an O-ring, and this has worked well. (Tip: If you find you need a little more belt tension to avoid slippage, try mounting the frame a little farther forward or backward on the Lab-Box. Or, wrap some rubber electrical insulating tape - NOT plastic “electrical tape”, which is too slippery - around the Lab-Box knob to make a “tire.”) Remember, as I said in the PDF, this is very much a “maker” project and you should feel free to adapt it to your materials and abilities. For example, if you,re good at 3D printing, you might be able to make parts that would allow you to use a toothed belt. If you do come up with any good variations, please post them!

@@jlwilliams Hi williams thanks to your work I started a project to motorize the lab box with the help of a friend ( is a 3d print designer.) work in progress... stay tuned:-)

Yes, it's a very easy build! It could be made fancier if the builder wants to -- for example, add a timer or a more sophisticated way of attaching it to the Lab-Box. But I wanted the basic version to be something that can be built without special tools. About the pulley: The PDF file linked in the description includes a complete parts list, and the ServoCity website has dimensioned drawings for each part. The complete pulley assembly (pulley plus the hub used to attach it to the motor shaft) is 14mm along its axis.The alignment isn't very critical -- during assembly you just slide the motor back and forth on the frame until the pulley is centered over the knob of the Lab-Box -- so if you have a different motor or different pulley that you would like to use, I'll bet you could make it work!

Yeah, I looked around and see what you mean. I figure we're victims of COVID-induced component shortages! The closest I could find was this one, and it's on backorder: www.youdoitelectronics.com/actobotics-o-ring-pulleys-1od-5-id-615130 If you don't want to wait and see, you may have to adapt the design. Remember, you can tweak motor voltage to get the rotation speed you want, even if you have to use a different-size pulley. Mind you, I HAVE NOT tried any of these suggestions, but... -- Order the 2-inch pulley from Servo City. -- See if one of these sewing-machine pulleys might work: electricmotorwarehouse.com/sewing-machine-motor-o-ring-pulley-7-8-od-x-1-4-bore-1x459/ -- Try one of these V-belt pulleys: www.zoro.com/congress-12-fixed-bore-1-groove-standard-v-belt-pulley-150-od-ca0150x050/i/G4447197/ -- I wonder if a plastic pulley such as one in this Tamiya kit could be made to work: www.pololu.com/product/109 Good luck and be sure to post if you find a good solution!

It's no different from using any other plastic tank in a water bath. From the photos you might think the black base of the Lab-Box is very thick and might act as an insulator, but it's actually open on the bottom so water can flow in and warm the reel compartment. I just put the Lab-Box in the bath at the same time I put in the solution bottles, and let them come up to temperature together; once everything is at the same temperature, there is no reason for it to change as the solutions go in and out. I don't worry about measuring the temperature inside the tank, but someone who wants to do that could use the new Lab-Box Pro Lid, which has a digital thermometer built into it. You can see more of the process in one of my other videos: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-UGhKU54E_ow.html

When you put the LB in a warming water bath to maintain color process temperature, you are going to soak the metal parts and blade which cuts the film from the 35mm cartridge. The problem is that the maker went cheap and didn't use a good stainless steel blade, so it will rust. You cannot open that conveniently to dry the parts and blade. Within the first year, LB users were complaining about rusted film cutter blades jamming in the mechanism. So keep your powder dry, guy.

It was kind of hard to figure out how to make it (I made lots of cardboard mockups) but now that the design is sorted, it should be pretty easy to put one together. The motor part is easy... the trickiest bit is getting nice sharp bends at the right places in the frame, but that's just because it's metal. It won't surprise me if people figure out how to make a workable frame out of hardwood, 3D printed bits, or even Legos...