It's growing up without Sky TV

Thanks mate, you've got one up on me, I know nothing about physics and nothing about programming

Hello over there. Thank you, it makes me happy to hear people from all over the world enjoy our videos. You're in luck, I'm actually working on the schematic of the breadboard version at the moment (in kicad so it'll be loads easier to read than the human man's scribbles), so hopefully I'll have that and a full parts list to go along with it very soon! But yeah I can go through the schematic for the budguter PCBs as the human man makes it. It's a bit of a mess and over a few pages and a bit different from the breadboard one in the videos but I'll do my best. And thanks for the heads up, all changed now.

you could use a cap to debounce the button but, this would restrict you to a very slow clock (a few Hz). The problem is, using just a cap you'd have to hold the preset on the 74hc74 active for the whole time the button bounce noise is present (~a few ms) and this would decide the upper limit of clock speed. But by using the debounce circuit in the video, which only holds the 74hc74 preset active for a time period in the order of pico seconds let us use the full clock speed of the Z80 (or in other words our max clock speed is no longer limited by button bounce noise). There are loads ways to debounce a button (remove noise from a signal) this is just the one they used on the Altair 8800. Hope that makes sense :)

@@DrBudgieandtheHumanMan oh thank you very much for this very detailed explanation

There's a very good reason for that... I don't have any haha. But you can build it with a 555 if you want, there's no rules here!

Thanks mate! Don't worry we got ideas for years!

yeah the list components got a bit long and the human man moved around quite a few of the passives in between videos and couldn't remember the values used from the previous video so I just listed the ICs (the exact values of the passives don't matter all that much, you can quite easily find 'good' values for them using a bit of trail and error). I am intending on putting our projects on GitHub (or something similar) but it's just finding the time to set it all up, but I will at some point :)

Thanks mate, you're too kind! I'm learning while making these videos and I always learn better with practical examples, never been very good at reading books (I got wings so can't turn the pages). Nah not a professor, just an unemployed budgie and an unemployed human man in a shed. We've got fancy bits of paper that say we can do stuff, but academia was sooooooooo boring, as soon as we got our certificates we ran, we ran fast. Thanks for your support!

That's great! If you need any help just ask :)

Thanks mate! Glad you found it useful, practical examples always help me understand stuff way better than books. There's no substitute for just typing some code, running it, getting a load of errors and then repeating the process until it works. (sorry for the late reply, I had a couple of days off).

Haha thanks mate this gave me a laugh. There'll be another video on the Altair project soon!

thanks mate! Glad you liked it!

I did hear that Schrodinger could never decide if his PS1 was on or off, it somehow existed in a state of both on and off at the same time!

Haha. He did try but he spilt a washing-up bowl full of coke on his PS1 so he couldn't finish it!

Haha, I don't know, I didn't plan on making kits but I guess if enough people are interested I could put PCBs or kits on Tindie or something.

@@DrBudgieandtheHumanMan Once my bank account recovers, I'll definitely buy one. Needs some Dr Budgie branding for the case.

@@DrBudgieandtheHumanMan I was quite keen on doing up a set of boards, but that front board looks expensive to have made up!

I'll need to do some/a lot of testing to make sure it all works properly, so it''ll probably be a little while before any kits appear. I could also make a single board version, it wouldn't have the capacity for expansion but would be cheaper to make. I'll have a think and try and come up with most cost effective solution :)

JLCPCB and PCBway are cheap(ish) both offer 100x100mm for ~$5 (US) but it's the post and duty that's sad, it's often more than the boards haha. But having a board that you designed made professionally is pretty cool!

whoaaa I actually taught someone something! Haha, I only found it out a couple years ago and by accident. You can do it on windows too! (well I've only tried it on Windows 10)

you're not proper scientist till you almost burn your house down a few times!

me and the human man had an interesting delivery from JLCPCB today! So there might be a sneaky peak of that and the enclosure coming out soon.

@@DrBudgieandtheHumanMan exciting!

Thanks mate, glad to hear you're enjoying it! The plan is to make a fancy front panel, we've got an old bit of lab equipment for the enclosure and we'll probably use some mild steel (as terrifying as it sounds, I'm letting the human man play with power tools) for the front panel and try and paint it up like a real life 70s computer! We've also got some fancy PCBs on the way too! Whether you wait till the end or get started now, I hope you do give it a go it's a fun build! :)

@@DrBudgieandtheHumanMan wooo. Fancy pcbs. That sounds amazing. The human man better watch out playing with power tools. I've been caught out a few times with z80 and 6502 builds on KZbin where people give up making them three or four videos in, but your approach here feels nicely fresh and from an electronics perspective - different! Keep up the good work.

Thanks mate! Ohhh right you want hardcore decoding. I'm not sure how a real engineer would do it, but this is how I would go about it. If I want the first 8k of memory to be RAM and the rest ROM: 1) log_2(8000) = 12.965... 2) the nearest whole number is 13 3) So I want the RAM to be selected up to address 0x1FFF (0001111111111111) and addresses 0x2000 (0010000000000000) and above to be ROM 4) So I'd OR together A15, A14 and A13 and the output of this would go to the RAM chip select pin and the inverse would go to the ROM chip select (assuming that the RAM and ROM had active low chip select pins). You can also OR the MREQ signal with A15, A14 and A13 to keep the IO space separate from the memory space. It gets a lot harder If you want to split the address space up further but it's a similar process, you just workout what address values you want your memory or IO device to be active between and use logic gates on the address bus to turn that combination of 1's and 0's into the chip select signals. You can get memory decoders which do some of the work for you and if it get really complex you could cheat and program a ROM to do the decoding for you. The address bus of the ROM connected to the Z80 address bus and then each bit of the data bus of the ROM goes to the chip select pins of whatever devices you're using. Hope this makes sense (a proper engineer would be able to explain this way better). Thanks, I'm slowly beating the cold! Haha

I can't blame you really, Bottom is the best! You could watch it and build at the same time! (that's how I fail exams).

Thanks mate! Seein' as yous like, asked so proper, I'll put it in the next video just for you! Ya know like at the moment it ain't actually got no decoding so the first 32k and second 32k are like the same innit. Look 'ere don't tell anyone else this, but rumour 'as that the human man 'as designed some PCBs with a fully decoded memory space, so you could 'ave 64k RAM or 64k ROM or 32k RAM and 32k ROM (where ya could 'ave RAM at the bottom and ROM at top or the other way round!)

I tried to scroll down in the PDF viewer.

you wouldn't believe the number of times the human man tries to click on/scroll stuff when he's editing these videos.

The other day me and the human man started screaming because we thought the computer had died (and we hadn't saved in ages), we were trying to scroll but it kept changing the volume! Then we realised VLC was in full screen and paused haha.

Sorry for my late reply. I'm really happy to hear that you got the first part of the computer working, good job! I tried to find the data sheet for the 74LC74 but the closest I could find was the 74LCX74 which is the low power (voltage) version of the 74 series chips, which operate at (Vcc) 2.5 - 3.3V, with 5V tolerant input pins (eg CLK, D) so it would in theory (with some minor changes to circuit) be possible to use the 74LCX74, with a separate 3.3V supply just for that chip, but I would make things more complicated. So I'd really recommend using the HC and AC variants of the 74 series logic (HCT and ACT would also work) used in this project, because I've only tested it with the HC variants. So I can't guarantee that it will work with other variants. As for the 74HC123, this can't be substituted with a 74HC138 I'm afraid, because the 74HC138 is a 3 to 8 line decoder and the 74HC123 is a "dual retriggerable monostable multivibrator". So they perform completely different operations so can't be substituted with one another. The debounce circuit using the 74HC123 could be substituted with an equivalent circuit using two 555 timers (or one 556). Is the 74HC123 difficult to find? I could make an alternative debounce circuit if this is the case. Super long explanation, hope it all makes sense :)

@@DrBudgieandtheHumanMan This is super helpful! Looking around online for information was a bit difficult for me. These chips aren't to hard or expensive at all luckily. I just wanted to make sure I had the correct information before buying those smaller chips, just in case I had useable parts already! This has been a fun learning experience so far, thanks for the help! :)

You're welcome and many thanks for taking the time to leave a comment! I like the detail in the simulator, the person that made it even added sound effects!

@@DrBudgieandtheHumanMan You made me go on and buy the parts needed to attempt and replicate your build as a fun learning experience. Thank you for giving me the kick to jump into the deep end.

@@JuliaPOWERR Cool! It's a fun project and I learned a lot doing it (I made a prototype) and it also helped me better understand programming concepts! If you get stuck or need any pointers just say and I'll do my best to help! Happy building :)

Thanks for the comment! That's a very good question , I completely forgot to mention the power supply in the video. I use the 5V line from an old pc ATX PSU. Thanks for pointing that out, I'll talk about that in the next video :)

@@DrBudgieandtheHumanMan Id recommend a fuse or something as that line is very powerful and might blow things up easily

thank you :)

Thanks for your comment. Good question! In the game in the video it doesn't. But I did try to implement more realist physics using Tsiolkovsky rocket equation (with the thrust and mass of the real apollo LEM) but it didn't work very well and kind of broke the game. In the future I might try adding a simplified pseudo rocket equation and making the game have levels of difficulty. If you have any ideas on how to implement this I'd be more than happy to try them :)

@@DrBudgieandtheHumanMan How did it break the game? Was it too realistic and not fun to play anymore or did the lander just go all over the place? Tsiolkovsky should work, altough I'd leave gravitational acceleration out of it, as in just Δv(m) = Isp * log(m0/m). Ooooor you could apply g only to the y-axis component. To make it even more "fun" use g = g0(1 - 2h/R) Do you have a code repository somewhere?

@@Breuningable Sorry for the late reply, I didn't get a notification and only just saw your reply (I'm still new to this youtube thing). Many thanks for your input it's most appreciated. It was a bit of both, the problem was that I couldn't find any data on the burn rate of the apollo LEM in any of the papers I found, so I just had to guess and it was quite sensitive to ∆m. So it either made very little difference to gameplay or made it uncontrollable (to much acceleration) and used an unrealistic amount of fuel, I just couldn't get the balance right with the real LEM + fuel mass (probably just my dodgy programming skills more than anything). But I didn't actually try Tsiolkovsky using the arbitrary fuel units I ended up using in the game (just giving the lander a mass in arbitrary fuel units). Also to make it even more "fun" the big mountain could apply g in the x-axis. I am going to try and setup GitHub and put all my projects on there, but it's just trying to find the time haha. But I will try and do it in the next couple of weeks :)

Thank you so much! Glad you enjoyed it!

Thank you so much for the positive comment mate! Happy physicsing!

Thanks mate, I'm so happy you liked it! There's plenty more insanity to come from me (Dr Budgie) and the Human Man, part 2 is out next week!

Wowwwwwww my first ever comment! Thanks mate, really appreciate it! I'm not cool enough to use dark theme, that's for the pros