2010.05.25

Intervalometer Version 1.3

16.44.40 - Mark

I've been working on my home made intervalometer on and off for well over a month now. I bought the parts for it in early April, bounced between building the original version based on it's schematic and reading up and learning how to actually use 555 ICs in mid April. Finally got the first working version packed into an Altoids sized tin in a frantic morning on April 20th (written inside the tin since I was pulling it off between going to a class then driving 6 hours to go camping for a weekend) About a week after finishing it I got around to putting together a semi-decent time lapse video.

Homemade Timelapse TriggerPart of the reason I had held off on the time lapse is because I wanted this to work as a wired remote for my camera, rather than having to carry around a couple candy tins with switches and cables attached. This however has been my big problem.

The original schematic calls for a NPN transistor to work as the switch for the shutter release. When it's base is getting power, the emitter and collector are bridged and the circuit for the shutter is closed. Since the manual switches are wired in parallel, they can't override a closed circuit and are blocked until the base looses power - be it the few moments the 555 drops power or when the battery is disconnected. If I had gone this way I probably wouldn't have had a problem using it as a wired remote, but it is mentioned as a glitch in the original write up.

In my build however I used a PNP transistor, originally for no reason other than I had a bunch more of them than NPNs and they worked in the breadboard prototype. It's emitter and collector are still the connections for the shutter release loop, but those points are only bridged when the base is grounded. Unfortunately this was a somewhat massive problem for me. It not only blocked me from using it as a wired remote when powered off, the second it was plugged into the camera was the second it would take the first exposure. I could jerry rig it into working in my favor, but I wanted full control all the time.

At that point I started thinking about how to get that control. I first thought of using multiple transistors, looking into Darlington transistors or Sziklai pair, even started thinking of Logic Gates and building them with transistors. All it needed to do would be isolate the transistor from the circuit when the power was off. As I got frustrated with the complex schemes of using transistors to control transistors, I started to rethink the simplest approach of isolating the key PNP transistor.

A quick test on the breadboarded version, and just unplugging the PNP's base made it work with the parallel switches when the power was off. While I could have wired in and mounted another switch, I preferred simplicity, and a DPST switch was purchased to replace the SPST power switch. One side still for power, the other between the 555 and the PNP base. It's a good fix, and I finally feel good documenting my version.

In addition to my use of a DPST switch and a PNP, there are a few other changes I made. The first is the different selection of resistors. While the potentiometer and paired 100k ohm resistors remain the same as the original, I changed the LED resistors to 10 ohm (I wanted some more light coming off the LEDs).

Since I wanted a time lapse mode faster than once every 30 seconds or so, the fastest given by the 220uF capacitor (up to about 4 and a half minutes as its slowest), so I used a SPDT switch and 22uF capacitor to add in a second mode that can shoot as fast as one exposure every 9 seconds (which goes up to ~30 seconds).

I also changed the .1uF with 33k Ohm resistor to a 10uF capacitor and 470k resistor. The original design didn't allow my Canon XSi enough time to run the shutter. This my change is a particularly long break for the shutter trigger, about a full second. While I originally only changed the resistor for a sufficient delay, I realized that the SPDT switch with the key capacitors, really had three positions.
Intravolimeter Schematic
This switch happens to have ON - OFF - ON positions. While I only cared about being able to switch the 2 key capacitors, when testing it I accidentally had it on the off position. When I powered it on it started running the shutter faster than once a second. While I may not be getting this right, when the one of the 2 larger capacitors are connected the circuit is monostable, a quick burst for the transistor, then starts over. When neither large capacitor is connected however, it starts running as a bistable, or flip-flow, circuit, opening the shutter loop for a second, then closing it for a second, with it's pace set by the small capacitor and resistor. While I have yet to find a real reason for this feature, I decided to take advantage of it and added the 10uF capacitor. So, if you follow this design, this gives the camera shutter a full second or so to run when it's in Monostable mode, and get an exposure every 2 seconds or so when in Bistable mode.

While I'm sure there are other changes that could be made, I think I'm done with this one (with the possible exception of designing a real circuit board for it). Between arduinos boards and the parts for building a Camera Axe, I think this will suit me well for a carry around wired remote and intervalometer.

If you want to build one for yourself, feel free to work off my schematic (image above, enlarged, or EAGLE Schematic) put it's still a good idea to refer to the article I worked from in Make Volume 15 or the extremely useful discusion thread on it's Instructables page.

The components are all from Mouser, but I got the perf board from Radio Shack. You can get all the parts there as well (in theory) but they charge a lot for the things they do stock, and sadly my local Radio Shack's component area is a sad disorganized mess. Of course Digikey is on par with Mouser (just a bit harder to navigate) and in this case everything you need (including perfboards) can be purchased at All Electronics (which just takes a good bit of hunting) It's worth nothing however that you can scrounge together a lot of these parts from old electronics.

555 Timer IC Based Intervalometer Part List
Parts
Needed
Part DescriptionPrice Per Part
11M Ohm Potentiometer$.80
1DPST Toggle Switch$1.24
1SPDT Slide Switch$.75
2Tactile Switches$.31
2Tactile Square Caps$.15
2LEDs$.08
1220uf Capacitor$.14
122uf Capacitor$.10
110uf Capacitor$.06
1555 IC$.31
1PNP Transistor$.11
210ohm Resistor$.10
2100k ohm Resistors$.10
1470k Ohm Resistor$.10
12.5mm Stereo Plug$1.55
19v Battery Snap$.38
1Multipurpose PC Board$1.99
Hookup wire
Solder (you should have it)
Enclosure (I used an altoids sized tin)
Total:  $9.01 + taxes and shipping

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2010.03.29

Inked all over

23.27.32 - Mark

Last week I posted Inking, part of it my history with screen printing shirts, part as attempting a short timelapse video of preparing the negatives for a few screens on some vellum paper. Aside from my own screw ups, the the DIY Screen Printing Instructable was a good resource I used though the entire project. However if it's your first attempt, don't start with your favorite project.

The first of the four screens I did ended up with a lot of pinholes in the screen's mask after washing it up after exposure. I was also stupid enough to ignore the pinholes and do a test print.

Pinholes in Screen Print MaskTest print with pinholes in screen print mask

A small art-style paint brush and more of the photo emulsion goo I was more or less able to remove the pinholes with a couple passes. Once it was done I started preparing the other three screens. However these I either spread on the wrong amount of goo and fell though, or the goo had been partially processed with light and didn't expose. In either case I only noticed it after I checked the dried screens, and the holes were too great to bother repairing, so they all got a heavy bleach water wash and a fresh round of photo sensitive emulsion (this sort of screw up and I was extremely pleased with using the homemade mix of Potassium Dichromate and Elmer's Glue instead of buying commercial products.)

The second batch worked and I applied the art, then set off to printing, and learned another lesson (or three).

First don't print them by yourself. In the past, I didn't print more than one or two on my own. I either paid for a company to do the prints or worked with a friend to make the prints. In this case I did 36 prints (9 of each screen), and it would have gone a lot faster if I had an extra set of hands to handle either the fabric or manage the screen and ink.

The other lessons would be a good workplace with good tools. Since I didn't have a table that could be used, and raining like crazy outside, I made the prints on the floor. Works well enough for small runs, but as many prints as I did it wasn't comfortable. Same sort of goes with tools. While the kit I had / made was fine, I needed the ink to dry before I could stack it. Without suitable shelves the "solution" I should have worked on setting up a drying rack or a heat treating system. C'est la vie.

Despite all these problems and lessons, and a couple mistakes on the flags I was printing, all 36 are good enough to use, since the friend who asked me to do all this work was half expecting to loose 5 or 6.
Most of the 36 prints made in this project

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2010.03.18

Inking

20.34.11 - Mark

A few years ago, one of my brothers bought a screen printing kit, the two of us figured out how to print some t-shirts, and planned on doing more with screen printing. Didn't quite happen. The parts have been reused to projects, but screen printing fell off to the side. The cloth prints since then were either one-off with freezer paper stencils and spray paint (similar to this project), experiments for other techniques, to simply being large enough that a professional lab felt more practical than an attempt at DIY printing on a short time table. However, about two weeks ago a friend asked me about printing some flags.

He'd used professional printers before, but the low number and small size meant it would have been pretty pricy, and while at first I figured stencils and spray paint would work (and it would) the numbers are enough that DIY screen printing would be easier. So I started working on the kit.

Unfortunately parts of it didn't age well. The screen, ink, and tools are in good enough shape, although quite probably not enough, and the photo sensitive emulsion chemicals were either missing, or used. I was also missing the manual. I know, oft ignored, but if you're playing with chemicals its wise to do your research. In this case I turned to Instructables, and landed on the true DIYers screen printing project. While it isn't the most precise article, it's a great guideline, both for people doing it themselves and those who want to save money.

So while I was waiting for the Potassium Dichromate / Elmer's glue photo emulsion to dry onto the screen, I started working on the art. In the past I'd dig up a piece of transparency sheet and use that for the mask, but finding any, and not liking the price I deiced to try vellum paper (in large part due to the DIY screen printer instructable). Which gets me to this video.

Since I'm working off a vector art piece, I wanted to print it on to the vellum. However my printers don't run on cheap ink, so I only printed out the outline, and would fill it in by hand. Right before I started filling it in I pulled out my old point and shoot and set it up for time-lapse.

Nice short and simple video, in many ways very similar to the Pennies video I. [wow, over 4 years ago!] The slight difference is I had the camera set on time lapse, in one shot a minute factory issued mode, so this ends up being choppier than I'd prefer. I'm not sure if I want to blame my lack of (good) camcorder, better knowledge of the CHDK hack for my point and shoots, or the extended lack of a intervalometer controller for my DSLR (be it commercial product, graphing calculator, arduino based project, or a crude but simple 555 electronic circuit)

In any case

Inking (4.4MB 320 x 240 H.264 Quicktime)

Creative Commons LicenseThis work is licensed under a Creative Commons Attribution-Noncommercial 3.0 License.

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2006.02.23

LED Throwies

20.27.31 - Mark

I just put together an LED throwie. Ever since I first saw them last week I've been thinking about ordering up the parts and making myself a pile. Unfortunately I've got that student budget thing. However I'm a resourceful geek and managed to make one based on the things I had floating around the house (magnet from an old 40MB hard drive, backup battery from my graphing calculator, LEDs from a bulk lot of blue LEDs I got a while ago ) They are amazingly fun things, and pricing them I was able to beat the suggested price of $1 a throwie ($.80 for single LED, $1 for 2 LEDs) eBay is amazing. Even $80 is a little more than I really want to do on my own, but I'm letting one of my brothers take one to school. I might do it if I can get my final cost for tossable throwies under $.50 each.

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