a short but highly technical history of DRAM – dynamic random access memory! 🧵 pic.twitter.com/Er1tsEpnOu

— Tube Time (@TubeTimeUS) February 27, 2021

Great Twitter thread from our friend Eric Schlaepfer of TubeTime.us:

“A short but highly technical history of DRAM – dynamic random access memory!”

but first: dynamic?
static – a logic circuit that operates down to 0Hz clock.
dynamic – a logic circuit with a minimum clock frequency.

static RAM is made of two cross-connected inverters along with two pass gate transistors that connect and disconnect the memory cell to the bit lines. you need 6 transistors to make a cell that can store one bit of information.

dynamic RAM cheats a little and uses a capacitor to store the bit instead. over time, this charge drains away so you have to periodically read the current state and then write it back again. it’s like refilling a leaky bucket.

here’s a more detailed diagram of the basic DRAM cell (3 transistor). the bit is stored in the gate capacitance of transistor M3 (shown as “parasitic C”). M1 is closed to write to the cell and M2 is closed to read from the cell.

now back to the history: this is the first practical DRAM chip, the Intel 1103, which they introduced in 1970. it was expensive at 1 cent per bit (1024 bits total). that’s about $7 now. you’d need two of these chips to store the text in this tweet!

here’s the pinout. address lines, chip enable, data out (inverted?), data in, read/write, precharge (similar to a clock line), and then three (!) power rails: VSS=+16V!, VDD=GND (PMOS is weird) and VBB=+19.5V(!!!)

Originally tweeted by Tube Time (@TubeTimeUS) on February 27, 2021.

If you are selling electronics kits and are hand picking and bagging components you’ll know it can be a time consuming affair. Add to that the fact that each of your kit needs some wires cut to length and it can all get quite frustrating! This automatic wire cutter takes the pain out of adding custom length wires to your product.

Read more Automatic Wire Cutter — Tindie Blog

From MakersBox on Tindie:

Soldering Kit for Doctor Who Fans

Show off your Doctor Who cred with a DIY badge you can solder yourself. Powered by an Attiny85, lights and sounds like an 8-bit TARDIS. CR2032 Battery not included.

If you want to hack around with the communication protocol that USB Power Delivery devices use to negotiate their power requirements with the upstream source, a tool like Google’s Twinkie really helps. With it you can sniff data off the line, analyze it, and even inject your own packets. Luckily for us, the search giant made the device open source so we can all have one of our own.

Unfortunately, as [dojoe] found out, the Twinkie isn’t particularly well suited for small-scale hobbyist manufacturing. So he came up with a revised design he calls Twonkie that replaces the six layer PCB with a much more reasonable four layer version that can be manufactured cheaply by OSHPark, and swaps out the BGA components with QFP alternatives you can hand solder.

Read more: Google-Inspired USB-PD Sniffer for the DIY Crowd

Update from Jason at AtomSoft:

AtomSoftTech: New Stuff

I have a couple of new PCBs being made by OSHPark . They are awesome as usual and have kept up during this pandemic. Which is a tuff thing to do. The first PCB is my IOBuddy shrunk down to smaller size. Its called the AtomIO

As you can see from the render it has 3 Outputs (LED) and 2 Inputs (BTN). It’s tiny as heck and will help keep breadboards less full. The LEDs are tied to GND with a Resistor so all you have to do is supply 2v to 6v to turn them on. The buttons are pulled low via 10k – 22k ohm. So when pressed they output a HIGH signal. What ever is on the power rail it is connected to.

The next board I have on the way is more of an internal use PCB but may sell it if wanted enough. its a simple breakout for those memory LCDs from sharp. The LS027B7DH01 to be exact. I call it the AtomSharp.