Dr Who : Lets Kill Hitler

Are you kidding me?

This show used to really be quite perfect. The characters made sense and they were properly motivated, the stories were tight and didn’t have many plot holes and it was all very fun and compelling to watch.

The recent episode just showed so clearly why Steven Moffat has ruined all of that. I’m not going to get very deep here but lets just start by talking a bit about the Hitler part of the episode. Ok, fine, we’re going back to kill Hitler. Nevermind that the doctor would never agree to this since it would alter the timeline in some seriously significant ways as any time traveler with even a bit of morality would agree with. Oh and yes, he had a gun pointed at him so maybe he agreed for that reason? The Doctor would have said at least something like “No guns! I hate guns!” and talked the girl out of the gun thing. Whatever..

So they go back and put Hitler in a closet. Never mind that they never let him out and never give him any explanations of why they are there or anything, forever leaving his timeline altered.  This plotline was pointless and used just as a vehicle to hook up the Doctor with these other time travelers who apparently go back and punish people who did bad deeds.. Silly but, ok, I’ll buy it a little bit.

Then River Song, who, I love. She really makes me tear up sometimes. This story line is really important to me but to throw in this whole line about her being that other girl and Rory and Amys best friend who you never heard of? Come on! That’s so lame to just add her like that!

And so she regenerates into River and tries to kill the Doctor who thwarts her every move but the poisoned lipstick. Um. Where did she find that? In Hitlers closet? No, she just had it.. apparently that was part of her regeneration. Come on again!

So the Doctor is later saved by River by her giving all of her tardis regeneration energy away to the Doctor. The jury is out for me here. I don’t know if this is ‘realistic’ or not or even possible but I’m ok with it.

Overall, it was cool from the River Song storyline perspective and that makes me happy but the absolute disregard for reality in the other story lines was pointless and sloppy and offensive.

I really hate Steven Moffat and what he’s done to my series!

Maybe I found him

So the package from Eletronix Express came in today. In it was a new DC power supply and 1/2 of the relays I ordered. The other 1/2 is coming from another vendor.

I hated almost all of them until I found this one. It made a lot of noise, it has a clear case, it’s 5V and it’s relatively cheap (2.50 each).

Unless I find something amazing in the next order this is going to be the relay I use. Stay tuned!


Today I ordered about 20 different types of relays. I’ve got to find the one we’re going to use since we need to know the size and voltage and resistance, etc. The big problem is that the one I want is about $5 in bulk which means about $160 in relay cost alone for one bit of the ALU which is a lot of money. The ALU isn’t fully designed yet since I need to figure out the control and I/O board still but I’m guessing that total we’re going to need about 200 or so relays. So my target price per relay is more like $1-$2.

Another relay requirement is that they make a good amount of noise since this is the whole reason for this project (to make a cool clicking computer). Also we want to mount them on a PC board without needing to add sockets for each one. The sockets, while cool and useful, would add even more cost. I’d like to also keep the voltage down to 5V or maybe 12V at most.

When I get the relays and start to play with them I’ll update you all.

Board Layout of the Adder

So now that I have the basic design worked out I now know that on each ALU board I will need to have 32 relays. I will also need to have an A input, a B input, a Carry in input, a Binvert input and a 2 bit input for the operation ( to select the 3Mux). Also I’ll need an output for the Result and the Carry Out. The board will also need power and will also have LEDs on the front to indicate the values of all the inputs and outputs.

Laying out where the Relays are going to go on the board is really hard since I’m doing it by hand. I know there’s probably some software tool to help me but I don’t have the energy to find and learn one. I’ve decided to go by hand instead and I’ve made up some sheets with 30 squares on them to help me out. Yes I know I need 32 relays but I ran out of space on the page.. 30 is good enough to get a good draft..

In laying out the relays I’m trying to minimize the signal path between the outputs of one relay/gate and inputs into the next gate/relay. I’m also trying to keep the board wiring at a minimum. Lastly I’m trying to keep the relays grouped into their functional gates (for cleanliness and organization).

I’ve spent about 2 hours so far on this and I’m not anywhere near where I want to be. For instance, here is a draft of the Adder Layout (10 relays) :


It’s not the best scan but as you can see the A and B inputs are at the top along with the C/I input and Sum out. C/O is in the middle. If you look back at the logic diagram for the Adder, you’ll see that we start by putting A and B into an XOR to be the first input into the second stage XOR for the Sum and also the input into one of the AND gates (to determine the carry out). I have this first XOR right at the top left and it feeds into the second one to it’s right (note that the XOR gates take 2 relays/boxes each). The output also goes into the AND gate directly below it.

The A and B inputs also feed into their own AND gate which is on the left side of the drawing. This is where we’ll need to do some wiring to stretch the A/B inputs over to the AND along the side. That AND and the other AND both feed into an OR. Note that that’s at the bottom of the drawing.

So this design packs the relays into a fairly organized square (plus one outlier on the top right) and has most of the inputs and outputs all lined up.

Now we have to fit this into the overall ALU board design.

Relay Notes

If you’re following along at home here are some initial notes and designs for the ALU portion of the computer.

First up is this sketch of how relays will be used to create the various gates used. There is an inverter, a 2 input AND, a 2 input OR and a 2 input XOR. Making the 3 input versions of the OR and the AND are easy in that you simply add another relay in series or parallel as indicated.

Next up is my design for the full adder. This is a traditional design using 2 XOR gates, 2 AND gates and an OR :

Next is a 3 input Multiplexor. This will select an input (A, B or C) using the S0 and S1 inputs. This is a big unit and uses 16 relays to do its job:

When we put all this together we have the basic logic design for one bit of the ALU. There will be 4 of these units, each one on its own board in the ALU unit.


I’ve been wanting to build something cool out of relays for a really long time. I was originally inspired when I was reading the book Code by Charles Petzold. Then a short time later I ended up taking my favorite class ever which was a hardware class focused on CPU architecture when I was studying for my MS. I decided then to build a computer out of relays. Sadly the cost was going to be prohibitive so it was limited to a bunch of drawings and notes.

But the time has come to start this project. It may take years to complete but every journey begins with a first step and I’m taking it!

My friend Troy has agreed to help me out and he’ll be documenting the project here on this blog. But I wanted to at least mention that we’re going to start. I’m quite excited and I’ve started sketching out some designs for a 4bit computer with an accumulator design. The ALU will be the first part we’re going to build and I’ve got that mostly designed already. It’s looking like 100-200 relays, which, plus other parts is going to run me over $1000. And this is just for one part of the computer!

Stay tuned for some scans of the notes and stuff!


I used to be a really healthy person. I was active, went to the gym, climbed rocks, was never in the hospital for anything except a couple of broken bones years ago. Then back in December I bent over to pick something up off the floor and boom, my back had this amazing pain. That pain, once it went away was replaced with a pain in my leg that made it so that I could barely walk at times.

That pain (I later learned it was called sciatic pain and caused by one of the discs in my spine herniating out of its natural spot and then pinching the sciatic nerve) stayed with me for about 8 months. It totally changed me. I was limping all over the place, I was in pain all the time, I was essentially disabled. I couldn’t sit in places for more than a few minutes, everything suffered.

I saw doctors. I tried yoga, physical therapy, epidural shots into my spine and 4 trips to acupuncture. Nothing worked. Finally I saw a surgeon and he explained how he could help me by doing a micro-discectomy. This is where they do a ‘simple’ procedure where they cut into your back, take out some spine bone, move the nerve over and then clip out the bulging part of the disc. I can’t tell you how afraid I was of this procedure. I could die, become paralyzed, or worse yet, it may not have worked. But I had to do it. Nothing was really helping the pain and I was at my wits end. I couldn’t take it any longer. I scheduled the surgery.

Of course I didn’t plan on breaking up with my girlfriend before that happened. Historically I am very, very bad at being sick. I fall apart and need my partner to totally take care of me and nurse me along until I’m better again. Now having to go through surgery alone was going to be even harder than I had expected it to be. And I had expected it to suck a lot.

I did it on one Friday. And I expected to be back at work the next Monday. My doctor assured me I’d feel some pain but be ok to go back to work and to recover alone. Of course this was far from the case with me. Luckily I had friends who insisted they would take care of me. The first week was terrible. Not really the pain, but getting over the anastasia and pain medications. They really did a number on me and I was a depressed mess and had various other physical issues as well. I literally contemplated suicide over being broken up and alone and I had a couple of serious meltdowns. Note to everyone, don’t go through surgery alone! Thank goodness I had people checking on me all the time.

After a week I was feeling a bit better and I wasn’t being as careful as I could have been. I’d been told not to bend over and to not lift anything over 10 pounds. Of course I did both. 8 days after my surgery I woke up and my leg pain was back completely. Did my lifting do it? There were only 2 occasions where I’d lifted things and they were both fairly minor but the timing was right. Nobody could say for sure.

Another week passes and I’m convinced I’d re-herniated my disc. The doctors don’t agree and tell me to rest and take it easy. They say it’s just part of the healing process. Day 15 I literally cannot walk without extreme pain. Day 16 is even worse. I am a wreck physically and mentally.

I go to the ER and spend 8 hours there before they give me an MRI. 2 hours later the preliminary results are that I have re-herniated. For the first time in 10 days I actually feel good because I was right. Everyone I knew (doctors too) were certain I was fine. I knew better. I speak to my surgeon the next day and he says I should go back to surgery in 4 days.

At this point I’ve been through literal hell. It was the worst 2 weeks of my life. All the pain, all the tears, all the missing of my work, and falling behind in my life, everything has been almost too much to bear. And now I’m being told I have to suck it up and do it all again.

That was one week ago today. Last Friday I did indeed go back and do it again. I haven’t been home since. I at least knew this time to limit my pain meds and I’ve taken almost none since Friday. I’m at a friends house since I know being home alone is not good for me mentally. And I’ve been religious in focusing on nothing but distractions. I’ve watched more tv and movies than I ever have before and done little else.

But there’s a small problem. If I re-herniate I’m told that I will have to do a way more serious surgery next since there is no more disc to spare in my L4-L5 space. If I have to go again, they do a full discectomy and they remove it entirely and replace it with a substitute. But that’s not good enough. In addition they will need to go in through my belly as well as my back. They will need to fuse my vertebrate together with a piece of bone from my hip. Instead of the 2 week recovery, it’s 2 months. Instead of a little pain and suffering, it’s a lot.

So you can imagine how I feel right now. I am terrified. I can’t even imagine living any kind of normal life again since at any moment I could re-herniate my disc. Sure the next month is really scary since when I’m not healed the chance is greater, but there’s the rest of my life to worry about as well. Who’s to say that in a year when I lean over to pick up a pice of paper from the floor I’ll do this all again?

All I want is to be healthy again. I want to live my life again. I want to not be in fear or in pain or disabled for the rest of my life. I’ve been a really good person in so many ways all my life. Why does it feel all of a sudden that I’m barely able to keep my head above the water? What did I do to deserve this fate?