74xx Competition! Part 1

As some of you may know, Dangerous Prototypes is putting on this big competition out for circuits that use discrete logic chips like 7400's or 4000's. In case you haven't seen the prize list, I suggest you cruise on over the dangerousprototypes.com and check it out.

         A while ago (in sixth grade) I built a rocket launch controller exclusively out of 4000 series chips and  555 timer. It was all on a breadboard and pretty messy. Now, in ninth grade, I've decided to get it back together, but this time on a PCB. But wait, there's more! I'm etching it myself, so it has to one-sided. Yes, there will be some jumpers, and the 555 will be replaced by an ATTiny for controllability and simplicity, but the displays and such will all be discrete. The first part I'm etching is the ATTiny and 4017 circuit. It will drive a bargraph display. Later, the divide-by-ten output of the 4017 will drive a 4026 [EDIT: 4029] (BCD count-up/count-down), which will drive a 4511(BCD to seven-segment display driver), and another 4017, the tenth output of which will trigger a relay and thus the rocket. In case that doesn't make sense, here's a super-simple diagram:

Sorry for the poorly drawn lines...

Programming the ATTiny85, Arduino Style

    This is a sort of a continuation of the last post. In the last post, I showed how to load the ATTiny85 cores into the Arduino IDE. If that worked for you, cool! This how to actually program the chip. If it didn't work... put a comment somewhere. I'll try to help.
    Anyway, programming the ATTiny is very easy. The only thing you really need to do is set up a target board. This is either a breadboard, perfboard, or PCB circuit that interfaces the ATTiny to an Arduino board. The circuit should have these connections:

This is called ISP circuit. The chips communicate over
SPI via this configuration.

Learning a Good Lesson the Hard Way

This week, I made a PCB on which I was going to put some LED's and a little microcontroller. However, when I got one part of it soldered and tested it (always a good idea) I found that the LED's hardly lit up. I could see them turn green, but they weren't casting any real light.

Here all the through-hole components are soldered on the
board.

Using Arduino with ATTiny's

    I really like the Arduino IDE. I also like the language that is much simpler, if less powerful, than the common Assembly/C code for other AVR's. However, Arduino uses a very limited chipset. You can use ATMega168, ATMega328, ATMega1260, ATMega 2560, and thats about it. Many times I want a lower cost, smaller form-factor chip for a project. The ATMega chips have lots of memory, interrupts, timers, and suchlike, but sometimes that's overkill. That's why I like to use the ATTiny line.

A flock of three ATTiny85's and an ATTiny 2313 with a lone ATMega328 outside.