On the trail of digital camera circuitry: ELV Digital Experiment Board DEB 100

You don't need to understand the details of digital camera circuits, like those found in the Canon T90 or Minolta X-700. Neither as a user nor as a DIY repairer.

It's enough to say: "The electronics reside in the small black blocks on the circuit board. Conductor tracks and cables connect them to the camera components. The electronics either work or they don't. What happens in detail is irrelevant." It's the same with dishwashers and smartphones.


However, if you want to understand how digital circuits work

you have to familiarize yourself with the basics of digital electronics.

This seems technically and abstractly complicated, but it's surprisingly simple when you immerse yourself in the binary world, which consists only of 1 or 0, high or low, yes or no.

There are good books on the subject.

Practical exercises with digital components such as logic gates, flip-flops, or counters are somewhat confusing, as you have to make many connections on the breadboard.



This is where the ELV Digital Experiment Board DEB 100 where basic digital circuits are already pre-wired comes into play.



You only have to connect the individual components via connectors to build circuits. Numerous switches, display elements such as status LEDs and seven-segment displays are also available. A detailed accompanying manual introduces the topic.

This allows you to work through the fundamentals on which digital camera circuits also function.

The next step is to work with microcontrollers, which can be programmed and contain these basic circuits as virtual units in a single component. This also makes newer SLRS and DSLRs more understandable in their operation


(German)

Hah, that's nice, those kinds of boards/kits used to be quite common once upon a time, especially in the1 1980s-1990s. They went out of fashion with the advent of microcontrollers and ASICs.

Andreas Thaler said:

This also makes newer SLRS and DSLRs more understandable in their operation

Click to expand...

Only to an extent, since these rely on highly tailored/application-specific controllers. Some of the principles used are the same as in generic microcontrollers, but the controllers in cameras (both analog and digital ones) involve a lot of black box behavior that you really can't fathom without company-internal documentation. How metering is handled, how shutter speeds etc. are generated and of course in DSLR's how image data are processed are all proprietary, black-box elements that we often don't even know to what extent they're implemented in hardware or in software (firmware).

koraks said:

Hah, that's nice, those kinds of boards/kits used to be quite common once upon a time, especially in the1 1980s-1990s. They went out of fashion with the advent of microcontrollers and ASICs.



Only to an extent, since these rely on highly tailored/application-specific controllers. Some of the principles used are the same as in generic microcontrollers, but the controllers in cameras (both analog and digital ones) involve a lot of black box behavior that you really can't fathom without company-internal documentation. How metering is handled, how shutter speeds etc. are generated and of course in DSLR's how image data are processed are all proprietary, black-box elements that we often don't even know to what extent they're implemented in hardware or in software (firmware).

Click to expand...

I knew this would appeal to you

But it's true. The fundamentals of digital electronics remain valid, whether as a TTL (transistor transistor logic) component or as a virtual program.

The implementations of camera manufacturers must also be based on these principles

This is not very pleasing to programmers who believe that code is everything (I don't mean you of course.)

koraks said:

Hah, that's nice, those kinds of boards/kits used to be quite common once upon a time, especially in the1 1980s-1990s. They went out of fashion with the advent of microcontrollers and ASICs.

Click to expand...

At least the right practice tool for 80s cameras.

And at least to get into the basics.

Although computers are already at work there, combining and condensing these basics into computing units („Rechenwerke“ in German).

Andreas Thaler said:

The implementations of camera manufacturers must also be based on these principles

Click to expand...

Well, yes, in the end they're also based on fundamental physics, Ohm's Law etc. The question is always what you want/need to understand for what purpose. Having said that, it never hurts to understand the basics of logic ports or how to work with a microcontroller.

Andreas Thaler said:

This is not very pleasing to programmers who believe that code is everything

Click to expand...

There's even an analogy within electrical engineering, where the analog people sometimes argue that all digital circuitry in the end is analog just as well. Which is very difficult to argue against, especially if you get down to the nitty gritty details of signal quality, HF etc.

Today I put the digital experiment board into operation. I'm using it to review the content of the course I completed some time ago.

The supply voltage can be selected between 3 and 15 VDC, and a power supply can be connected via a socket plug. Alternatively, three AA batteries can be inserted into the holder on the bottom of the board for 4.5 VDC.




The individual digital components are connected to each other via cable bridges.




Here, I've connected the two inputs of a NAND gate (CD4011) to the operating voltage via two push buttons.

I've also connected the NAND gate's output to an inverter (NOT, CD4069), thus creating an AND gate.




Both outputs are connected to LEDs that indicate the respective levels HIGH or LOW.




With this arrangement, the function table for two inputs can be switched with a total of four possible combinations.

Here are the two combinations B = 0 (LOW), A = 0 and B = 1 (HIGH) and A = 1:



Both inputs (B, A) are LOW, the buttons are not pressed.

This results in the NAND output above being HIGH and the AND output being LOW.




Both inputs are HIGH (buttons pressed) so the NAND output is LOW and the AND output is HIGH.


Logical circuits can be constructed using AND, OR, and NOT

This allows you to create the three logical gates AND, OR, and NOT using NAND gates and observe the individual switching combinations.

Since there are only four NAND gates on the board, additional inverters are provided for NOT. However, NOT can, of course, also be generated with NAND.

For example, in an experiment, an LED should light up when ASA = 100, EV = 12, and aperture = 5.6. If all three conditions are met via AND, the LED is activated.

This allows you to get a sense of the camera circuits, even if you don't actually construct the experiment and instead press buttons.




If you like lights, you'll get your money's worth here

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For me, the experiment board is a perfect complement to circuit simulation on the PC and studying digital circuits in books. You build circuits practically and have a tangible sense of achievement when something works.

You can continue working on the other digital components on the board and deepen your understanding. In any case, you get an insight into how digital circuits fundamentally work.

This should help me when familiarizing myself with the literature on the digital driven Canon A-1 and AE-1.