Converting A B&W Enlarger For Colour Analog Photo Printing

May 8, 2023 by 16 Comments

[Koraks tinkers] was gifted a gargantuan photographic enlarger, a Durst Laborator 138 s, which is a unit designed specifically for black and white usage only. This was not good enough for [Koraks] so down the rabbit hole of conversion to colour we go! The moral of the story is this: if you can’t find it, build it. The hacker mentality. After wasting time and effort trying to source a period colour head for the thing, [Koraks] did the decent thing and converted what was already in front of them.

A hacked Chinese-sourced COB array. This is no use.

Now, if you’re thinking this process is simply a matter of ripping out the tungsten bulb and sticking a high-power RGB array in there, then you’re going to be disappointed! You see, colour photography of the era — specifically the RA4 process in this case — requires careful colour calibration and is heavily biased towards the red end of the visible spectrum, due to the colour curve of those tungsten bulbs we touched upon earlier.

Attempt 2: With a heavy bias towards the red end of the spectrum

The first attempt at using an off-the-shelf COB array was a bust — it simply wasn’t bright enough once the light had passed through the diffuser plate, and the light path losses were too high to expose the RA4 paper sufficiently, especially at the red end of the spectrum. Quite simply this is due to the reduced energy of red photons (compared to blue) making the desired chemical reaction rate too low. The solution is more power.

Another issue that quickly raised itself was that 8-bits of PWM control of the RGB components was inadequate since the ratio of blue to red required was so skewed, that only a few effective bits of blue channel control were usable, and that was far too granular to get the necessary accuracy.

[Koraks’] approach was to custom build an LED array with twenty red 3W LEDs and eight each of the green and blue devices. 12-bits of PWM resolution was delivered via a PCA9685 PWM controller, that also handily controlled the cooling fans. The whole thing was hooked up to an Arduino Nano, with an MCP23016 expander board performing the duty of interfacing the rotary encoders and trigger footswitch. In fact, several iterations of the LED array have been constructed and this four-part blog series (Part1, Part2, Part3, Part4) lays out the whole story in all its gory detail for your entertainment. Enjoy!

COB LED arrays are pretty nifty, checkout turning them into 7-segment displays, just because. If all you want is raw power, we reckon that 100W “should be enough for anyone…”

Thanks [macsimski] for the tip!

Update: Corrected the article header from ‘exposer head’ to ‘enlarger’ for clarity at the request of the project author.

VCF East 2023: Alan Wolke On His Passion For Tech

May 8, 2023 by 3 Comments

If you’re one of the more than 180,000 subscribers to [Alan Wolke]’s YouTube channel W2AEW, you’ll know he’s a lover of old test gear and ham radio hardware. You may have followed one of his tutorials, or referenced his work while repairing or upgrading your own equipment. But when we got a chance to talk to him one-on-one during Vintage Computer Festival East 2023, we were treated to a more personal look at the man himself.

Like many of us, [Alan] says he got his start with electronics at a young age simply by taking things apart and trying to put them back together again. From there he got a job in a TV repair shop during high school, where he was able to hone his natural curiosity into a marketable skill. His career took him through several of tech companies, but he ultimately ended up in an engineering role at Tektronix, a position he’s held for nearly 20 years.

Despite continuing to stay on the cutting edge, it’s no surprise that he still has a certain attraction to the technology from his youth. But it’s more than simple nostalgia — he points out that vintage hardware is generally easier to service than modern gear. As many of his own videos show, there was something of a technological “sweet spot” around the mid-20th century to the 1980s or so; where you could expect to not only have schematics available, but the design and construction of hardware was such that you could still reason your way through it using basic troubleshooting principles.

As for being a ham, [Alan] thinks it’s a great way for get an even deeper understanding of technology. He says that if you’re interested in learning how electronics work, repairing and upgrading old radio hardware is a great way to flex your mental muscles. But at the same time, being a ham isn’t limited to dusting off war-surplus radios that were built before you were born. There’s plenty of ways to mix in modern technology, from digital modes to receiving signals from satellites using a software-defined radio.

[Alan] was just one of the fascinating people we got a chance to speak with during our visit to the 2023 Vintage Computer Festival East. We’ve still got more interviews to come, but in the meantime, you can check out our previous coverage of this incredible retrocomputing event.

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A Literate Assembly Language

May 8, 2023 by 80 Comments

A recent edition of [Babbage’s] The Chip Letter discusses the obscurity of assembly language. He points out, and I think correctly, that assembly language is more often read than written, yet nearly all of them are hampered by obscurity left over from the days when punched cards had 80 columns and a six-letter symbol was all you could manage in the limited memory space of the computer. For example,  without looking it up, what does the ARM instruction FJCVTZS do? The instruction’s full name is Floating-point Javascript Convert to Signed Fixed-point Rounding Towards Zero. Not super helpful.

But it did occur to me that nothing is stopping you from writing a literate assembler that is made to be easier to read. First, most C compilers will accept some sort of asm statement, and you could probably manage that with compile-time string construction and macros. However, I think there is a better possibility.

Reuse, Recycle

Since I sometimes develop new CPU architectures, I have a universal cross assembler that is, honestly, an ugly hack, but it works quite well. I’ve talked about it before, but if you don’t want to read the whole post about it, it uses some simple tricks to convert standard-looking assembly language formats into C code that is then compiled. Executing the resulting program outputs the desired machine language into a desired file format. It is very easy to set up, and in the middle, there’s a nice C program that emits machine code. It is not much more readable than the raw assembly, but you shouldn’t have to see it. But what if we started the process there and made the format readable?

At the heart of the system is a C program that lives in soloasm.c. It handles command line options and output file generation. It calls an external function, genasm with a single integer argument. When that argument is set to 1, it indicates the assembler is in its first pass, and you only need to fill in label values with real numbers. If the pass is a 2, it means actually fill in the array that holds the code.

That array is defined in the __solo_info instruction (soloasm.h). It includes the size of the memory, a pointer to the code, the processor’s word size, the beginning and end addresses, and an error flag. Normally, the system converts your assembly language input into a bunch of function calls it writes inside the genasm function. But in this case, I want to reuse soloasm.c to create a literate assembly language. Continue reading “A Literate Assembly Language” →

Hackaday Prize 2023: The Realities Of The Homework Machine

May 8, 2023 by 83 Comments

For those outside the world of education, it can be hard to judge the impact that ChatGPT has had on homework assignments. If you didn’t know, the first challenge of the 2023 Hackaday Prize is focused on improving education. [Devadath P R] decided that the best way to help teachers and teaching culture was to confront them head-on with our new reality by building the homework machine.

The goal of the machine is to be able to stick in any worksheet or assignment and have it write out the answers in your own handwriting, and so far, the results are pretty impressive. There are already pen holder tools for 3D printers, but they often have a few drawbacks. Existing tools often take quite a while to generate G-Code for long pages of text. Hobby servos to lift the pen up and down take more wear than you’d expect as a single page has thousands of actuations. Vibrations are also a problem as they are a dead giveaway that the text was not human-written. [Devadath] created a small Python GUI to record their particular handwriting style on a graphics tablet and used ChatGPT to generate answers. Continue reading “Hackaday Prize 2023: The Realities Of The Homework Machine” →

Ask Hackaday: Why Do Self Driving Cars Keep Causing Traffic Jams?

May 8, 2023 by 133 Comments

Despite what some people might tell you, self-driving cars aren’t really on the market yet. Instead, there’s a small handful of startups and big tech companies that are rapidly developing prototypes of this technology. These vehicles are furiously testing in various cities around the world.

In fact, depending on where you live, you might have noticed them out and about. Not least because many of them keep causing traffic jams, much to the frustration of their fellow road users. Let’s dive in and look at what’s going wrong.

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The Bicycle (and More) Explained

May 8, 2023 by 25 Comments

They say a picture is worth a thousand words, but an animation, then, must be worth a million. Make that animation interactive, and… well, we don’t know how many words it is worth, but it is plenty! That’s the idea behind [Bartosz Ciechanowski’s] blog where he uses clever interactive animations to explain the surprisingly complex physics of riding a bicycle.

The first animation lets you view a rider from any angle and control the rider’s pose. Later ones show you how forces act on the rider and bicycle, starting with example wooden boxes and working back up to the original bike rider with force vectors visible. As you move the rider or the bike, the arrows show you the direction and magnitude of force.

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Can You Use A POST Card With A Modern BIOS?

May 8, 2023 by 36 Comments

[Alessandro Carminati] spends the day hacking Linux kernels, and to such an end needed a decent compilation machine to chew through the builds. One day, this machine refused to boot leaving some head-scratching to do, and remembering the motherboard diagnostics procedures of old, realized that wasn’t going to work for this modern board. You see, older ISA-based systems were much simpler, with diagnostic POST codes accessible by sniffing the bus with an appropriate card inserted, but the modern motherboard doesn’t even export the same bus anymore.

See “out 0x80, al” in there? That’s a POST code being written

Do modern machines even run a POST test at all, or are there other standards? After firing up a Linux machine and dumping the first meg of memory address space, it clearly contained some of the BIOS code. [Alessandro] looked at a disassembly of the BIOS update image and saw a similar structure, with POST code data sent to port 0x80 just like machines of old.

But instead of an ISA CPU bus, we have the Low Pin Count (LPC) bus which is used to hook up the ‘super IO’ functions, controlling things such as fans, temp sensors, and other system management functions. It also serves as the connection for the TPM feature, which usually appears as one of the motherboard connectors intended to be user-accessible. It turns out that POST codes can be accessed from this point with an appropriate POST card that can talk LPC.

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