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Building a 2-bit A/D converter with LM339 comparators and 74LS00 NAND gates
Building a 2-bit A/D converter with LM339 comparators and 74LS00 NAND gates
By Julian
Youtuber, shed dweller, solar charge controller aficionado
Stereo ribbon from the 90s.
Yes I have a stereo from the 90s that has a bunch of that type of ribbon in it.
Thats neat. I made a similar circuit using a nand schmitt trigger. But this had a more sharp, tight voltage window. I believe the i.c. was a 74ls132. Dont remember over the years. Cool videos though, good work.
I am currently in "Julian" mode. I don't understand it all, but I know you will make it "click" for me. You describe and demonstrate electronics so well that I think if I was watching you when I was 13, I would know it now at 56. You help me to "see" the circuits.
Thank you so much Julian. It is fascinating to watch your vids.
I also built my first Digital Clock using ALL 74 series and 7 segment filament (!) displays. lol
Edit: It was 93 series of DTL!
When I was (a lot younger) I was in the RAF as an Air Radar Tech. Some one in MOD decided that radar was 1's and 0's and gave us the computer systems on a Nimrod. Sometime later after lots of PG studies, I ended up teaching my bosses Digital Computer Fundamentals. All NAND gate stuff! 1/2 full adder with carry was the final exam I set.
This was one of the first IC based circuits I ever made outside of the 555. I got the idea from using a free java based circuit simulator program called CircuitMod, which I HIGHLY recommend, btw. One of the example circuits was a flash ADC with pretty much this same layout, only with XOR gates for the logic, I believe. I didn't have proper comparators, though so I used 4 LM358 dual opamps as comparators instead. My initial version was more like a bar graph display driver, since I didn't put any logic in it to make the output binary. It only lit up the LEDs according to how much voltage was going into the input. I connected the input up to the capacitor on a 555 in astable mode through a mosfet buffer to provide a triangle wave type input to make the LEDs blink on their own.
I can't stress enough how great CircuitMod is, though. It's a huge reason why I got into electronics in the first place. The other reason being channels such as this one, Big Clive and EEVblog. But just being able to play with circuits without having to buy anything yet was great preparation for the real thing. Once I had learned enough from watching videos like this and playing with CircuitMod I finally made the jump to the real thing. It's a wonderful tool for being able to visualize what's going on in a circuit since it lets you see the path of the current(s) through the circuit, and the examples are great educational fun to play with. Has examples like PLLs, ADC/DACs, logic families with discrete transistors, various amplifiers, passive/active filters, RLC and other oscillators, etc. I probably learned more from that program than anything else, save for actual hands on experience.
Great video Julian, enjoyed it a lot. Can you do a simple DAC next, just for completeness?
Julian, you can do the decoding with just 4 two-input NORs, eg. one 74LS02.
MSB: B NOR B (just B inverted)
LSB: C NOR (B NOR (A NOR A))
This gives an inverted output s.t. you can attach the LED's cathodes.
Non-inverted output also works with only 4 NORs: (A NOR B) NOR (C NOR (B NOR B)) for the LSB; MSB is just B.
Thanks Julian for the video. I enjoyed it and learned something. Just how fast and accurate is this thing?
hello @Julian….can you give me your email adress….or just send me your MPPT arduino source code…thanks a lot
Or… Wire up the voltage divider to the opposite (+in) and pot to -in on the one that needs to be low (when high)
Uh, cant you just use another op amp to do some maths to get your binary..
How about try implementing a discrete Delta Sigma ADC?
Generate a sawtooth waveform with a couple of comparators, feed that into the main comparator input and you have converted an analogue signal to PWM. That's a really type of ADC and I think it should make quite an elegant circuit, being made of just comparators and passives (and a couple of diodes).
It is used in many switching power supply controllers to change an (approximately DC in the steady state) analogue voltage error signal into a digital signal to drive a FET switch, amplifying the power in the digital signal, then at the other end of the circuit the digital power is converted back to a DC analogue output voltage by an LC filter.
10 grope eneloops to 5th anniversary edition
Up to 10 comparators you can use LS147 (10-LINE-TO-4-LINE AND 8-LINE-TO-3-LINE PRIORITY ENCODERS) as a single IC logic.