This is another photo from our most recent trip to Cambodia. This one is from the temple Ta Prohm taken on our second day exploring. As you can see it’s gorgeous but that meant it took forever for us to get a clear shot of the door without other people in it. But overall, it was well worth the wait and I’d recommend it to everyone.
This is a super simple post to encourage you to use schematics when you use EagleCAD. When I learned, the person who taught me didn’t use schematics so I learned to not use schematics and just design the board using packages. At first I didn’t know any better and blindly accepted the occasional error that happened because I switched pins. It was especially difficult when the chip package is rotated from the documentation and gets even worse when it’s also on the bottom of a board. But in the last few months I’ve been burned several times by this and I’ve seen the light. From now on, I’ve started using schematics for all my boards. Compared to just designing a board from packages, doing the schematic first is a lot more work. But if you verify the package and schematic when you make it, it eliminates almost all of the errors. And while making the schematic and device is a pain in the butt, it makes laying out the board a lot faster because everything is already connected by airwires. Anyway, that’s my advice, take it or leave it, but I hope it helps somebody avoid the mistakes I made.
I was cleaning up my lab earlier today and found some old soldering practice boards and thought I’d share. This was from about six months ago when I needed to solder an atmega 2560 chip for a robot controller. I didn’t have time for mistakes so I sent it out to be made by Macrofab because I’d had a bad experience with the same chip in the past. There were some delays from Macrofab and I don’t like having to outsource things so while I was waiting I ordered six test boards from OSHpark and some chips and got to practicing. In this case the test chips were some random audio chip which at about $1/chip was the cheapest chip in a TQFP100 package (0.4mm pitch), which is the same as the ATmega2560. I messed up a couple of pins on the first two boards but the third time was the charm and all of them after that were perfect. The whole thing was much easier than expected and led me to try and figure out what went so poorly before. Turns out the previous attempts had been with a flux pen that was several years past expiration; such a silly mistake to ruin a board. Anyway, there you go with my little trip down memory lane.
My robotics class is in a unique situation in that we are using the Wallaby from KIPR as a robotics controller with the original version 1 Create from iRobot. Almost everybody else has moved on to the Create 2 but I’m not a fan and we’ve still got a lot of Create 1s around so we’ll use them until they die. But this leaves us in an interesting position getting them to communicate. This isn’t a super exciting post but maybe it’ll help somebody.
We’re using the Wallaby from KIPR in my robotics class this semester. I’d been told at the beginning of the semester that the pull-up resistors on the Wallaby weren’t working so many of our old bump sensors would not work. So, I made this quick little adapter board to add pull-up resistors myself. The pins are female headers that are extra long so that they can be plugged in directly without any other pins (I found them by searching for stacking headers). I decided to only do four pins so that the other slots could be left open for other sensors that might not want a pull-up resistor. If I did this again, I’d do only three or six slots since stacking headers are easy to find in those lengths; I used 10 pin headers cut in half and sanded flat. So there you go. Not too interesting but documented for anybody else who may want it.
This picture of a monk was taken on our recent trip to Cambodia. This monk sat on the steps in Angkor Wat and watched as the tourists explored and climbed around on the temple. I approached him and asked if I could take his picture but he didn’t seem to understand me. I gestured to my camera and then to him and he smiled and nodded yes and went back to watching the tourists. In a location of extreme chaos he was a beacon of calm that really stuck with me.
I started to get into home automation in the last year and because I’m an Apple fanboy I went with Homekit from Apple. The good part is that Apple tests every product to make sure they are high quality and don’t have vulnerabilities. But, this also means you get fewer products and you are at Apple’s mercy for abilities. Generally I like this walled garden approach but the most glaring problem is using geolocation triggers to unlock/lock a door. Continue reading “Homekit Geolocation Door Lock Workaround”
I’m a little particular about the products I use, especially those I travel with, and I’m always searching for the perfect stuff. I thought I had found the perfect toiletry bag last year but I became frustrated that my stuff got tossed around during every trip. So during a particularly boring day at the lab, I made an insert to keep things organized and save my sanity.
Here’s my schematic and board design for a simple low side switch using a N channel mosfet. It’s a simple circuit that has a input for positive and negative and an output for positive and negative connections. Pretty self explanatory. It seems like every time I go to work with mosfets I have to spend a good 5-10 minutes reminding myself how they work. So here’s a reminder to myself for the next time I go looking and maybe it’ll help somebody else out.
Here’s my schematic and board design for a simple high side switch using a P channel mosfet. It’s a simple circuit that has a input for positive and negative and an output for positive and negative connections. Pretty self explanatory. It seems like every time I go to work with mosfets I have to spend a good 5-10 minutes reminding myself how they work. So here’s a reminder to myself for the next time I go looking.