Category: Electronics

Free Stickers!

They just came in, while supplies last..get a free sticker!

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1. You have to have a twitter, Facebook, or blog/vlog that appears you have some interest in electronics, being a “maker”, or computer programming and your shipping address is in North America.

2. #tymkrs (irc) skip to the head of the line as long as they don’t wait more than a few days

3. E-mail or tweet @chasxmd your @ twitter_name or blog link.. and your shipping address to my e-mail address chas at this domain.. alternately see the full e-mail address on the right hand of this page under “Contact/Social”

Enjoy!

First try at reflow soldering with an 858D hot air station.

This is my first try at reflow soldering. It took four attempts to get it right… so you learn 3 ways not to do it 😉 I just got this 858D station in the mail the other day, it cost me about $70 on eBay.

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In this video I referenced Jayson Tautic’s reflow example.

A tiny Si4707 WX Radio Project Update

I pulled out the weather radio project today to see what I could get done in a few hours. I was pretty close on finishing off the hardware but I fell a little short right at the end. I found I had forgotten to buy something to convert the regulated 5V to 3.3V for the radio (and PIC since they’re tied together on I2C). I ran into a few issues I totally spaced:1.  The Si4707 requires a reset after power up .. it ignores I2C if you don’t.

2. Pull-ups.. duh, not only on I2C which I had, but don’t forget the Si4707 reset (oops).

I ended up buying a couple random Digikey parts at the ham radio convention and guess what? 10@ MCP1802T-3002I/OT (300mA 3.0V LDO) ..they are SOT23-5 and I had JUST gotten 10 break-out boards in the mail so I ended up having a 5V3.3V converter (close enough anyways, as the PIC and Si4707 work down to 2.7V).. soldered it up but I didn’t have time to pop it in. I used the Weller but I think I’m going to solder another one with the new hot air gun I got this week. I ordered one of those cheap 858D rework stations; I don’t plan on using it too much so hopefully it’ll do the trick. I also got a bunch of SMD protoboards.. so I get to practice reflow this week.

Tomorrow I should be able to finish up the radio and then it’s all software.

Si4707 WX Radio Build - 11MAR14

The photo isn’t the most exciting workbench shot but you can see that 858D in the back corner. The WX radio is the black box right up close to the left.

A weekend outside..

I didn’t have a very productive weekend in the workshop. I received a ton of parts Friday and Saturday including the case to the WX radio. I started installing parts and pieces in the case. I’m always very nervous about the first drill hole.. A only made a minor error (so far) and it is nothing noticeable.

I spent much of the weekend with my wife doing little tid bits outside the house. She spent a lot of time home last week so she was sick of being home; that directly translate into a reduction of bench time 😉 She did go out for a work thing Saturday and I went down to the Mike and Key game radio swap meet. I purchased a bunch of odds and ends and gave up when my pockets were full and I couldn’t carry anymore.

This morning we went out for a quick bit after sleeping in a little and went for a hike out east. It was relaxing but ate up most of the day. I suspect I won’t end up with a lot of bench time until this next weekend: I will likely have a bunch of overtime at work as I just inherited another project when I’m already way overbooked. I know, better than not having work.

Some of my purchases include a cheapo hot air gun.. For reflow soldering. I don’t know if I made a mistake going cheap? I also bought a new power supply and just a ton of parts. I pulled my last 16pin DIP socket out and can’t believe I didn’t order some last time?! How embarrassing! I also ordered six of the new TAUTIC 18F26K22 dev boards on Tindie and some blog stickers.. Check out those dev boards if you’re into PICs, their pretty slick.

I’ll leave you with a photo of the falls we hit up on our hike today…

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An evening of measuring inductance

I was inspired by Alan Wolke’s ( @W2AEW ) video on measuring capacitors and inductors with an oscilloscope. I tried it out and it works pretty reasonably; yeah why wouldn’t it? Anyhow, if you can do it on an oscilloscope it can be done by a microcontroller right?  I have been trying to keep myself from buying this $220 eBay LCR meter on eBay.. it looks nice enough (model: MCH2811C). I needed to make this a project or I was going to pull the trigger on some Chinese garbage!

I went with simple and cheap, I don’t know how well it’ll work out yet but I bread-boarded a proof of concept design. It tested okay after some modification. The first road bump was I had found the PIC output pins had unacceptable rise time compared to 74HC14. The first change was using the PIC output to drive the 74HC14 HEX inverter to get the quick rise time needed.  I’m throwing a fast edge at the tank circuit that includes an “unknown” inductor and then I do my measurement, just as Alan used his homebrew TDR circuit. I went really low tech on my measurement circuit, I may change this. I used an LM339 comparator and a trimmer as a voltage divider. The first couple waves in the tank “ring” trigger the comparator and I measure the frequency by figuring out the time between the positive pulses by timer. Pretty simple no? It works fine as it turns out. I will have to get a better capacitor and ensure I measure it very accurately to do my math in the PIC and get a reasonable result.

Instead of the usual photos I made another YouTube video. It wasn’t a great one, one take, no editing.. it’s gets my point across (kind of).

My project proof of concept for the PIC L-meter. With the addition of a known inductor and a rotary switch and a little more code you can turn this into a PIC LC-meter in no time.

 

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