HACK A WEEK

This week I assembled all the parts onto a perfboard after making a layout with ExpressPCB. I use the layout as a guide when assembling circuits on a perfboard. Once the circuit is proven to work I can make a PCB from the layout. In this case it’s only serving as a guide. After assembling the board and connecting all the external wiring and LEDs I tested the board out. I immediately found an error on pin 8 of the first 555 timer. I failed to connect it to the positive voltage rail! OOPS! After connecting pin 8 the circuit began to function but with a minor flaw. The LEDs connected to the drain of the MOSFETs are staying dimly lit between pulsing cycles. They should be out completely! This will require some troubleshooting on my part. The circuit worked perfectly fine on the breadboard. I’ll be double checking my schematic and the circuit and looking for a possible error. It could also be an issue with the capacitance of a breadboard. I’ve run into this type of thing before. Some breadboards act as a capacitor and can influence the behavior of a circuit.

It may be a problem with the way I’ve connected the MOSFET. Here’s is a great beginner’s guide to the MOSFET that helped me understand how they work.

If you have any thoughts on this problem and it’s possible cause please join in on the discussion on YouTube or here on the blog. Below you’ll find a schematic of the circuit, a picture of the circuit on the breadboard and of course this week’s video.

The schematic. You’ll notice that I have a PNP connected to pin 3 of the first 555. It’s actually connected wrong but it somehow works to turn on the third 555! I’m scratchin my head on this one. I’ve revised this several times and this the current circuit. I now have a BC547 NPN transistor serving as a inverting buffer. This works great to turn on the 555 but I still have a problem with the MOSFET connected to that 555. When it’s connected the flashing stops.

The breadboarded circuit

Keep on hackin!

I get a lot of email with requests to build circuits for people. Most are more than I would want to take on for a simple Hack A Week project without some monetary compensation but this one was unique. The email tells the story.

“Hey Dino,
I love your site and have a request if you are taking them. I’m member of a small volunteer fire dept. I’ve talked to many members of many fire depts over the years and they are always talking about where to get reasonably priced emergency response lights like Whalen or Code3 makes (they run in the hundreds of dollars from these companies). In our state the lights would be flashing red LED’s.

Thanks for taking the time to read this and all the great videos!”

How could I turn that one down? My first thought was to use the venerable 555 timer because it’s readily available and easy to use. Since I wanted two banks of lights to flash alternately I could use two 555s in astable mode and drive one of them with pin 3 when it’s off and goes low to ground. The first 555 would be driven by another 555 in astable mode oscillating at the rate of 1 hz.

Once again I referenced Rob Paisley’s awesome 555 timer page where you’ll find all kinds of info and applications for the 555.

I’ll post the final schematic, a PCB layout and a parts list in part 2 next week.

It all becomes clear in the video.

Keep on hackin!

Suppose you’re out on a hike or a hunt and you get stranded by weather and you have to just hunker down and tough it out. How do you start a fire to keep warm? Well here’s a great solution I learned from my Dad. He was an avid hunter and fisherman in the Adirondack mountains where I grew up and he showed me this when I was a teenager. These waterproof fire starters are easy to make and can be easily stashed in a back pack or jacket. No matter how wet they get they’ll still be ready to start a fire.

Follow along now as I show you how to make them.

Keep on hackin… and stay warm!

I received the tubes, a new phono cartridge and needle this week! After installing everything the sound was definitely better but the right channel is still louder than the left one. I pulled the amplifier chassis out and tested the capacitors. These capacitors are of the older paper wound variety and they have a tendency to dry out and fail. After I tested three with the results being bad I decided to just replace them all.

I started looking for these capacitors on the internet and found it hard to find them. They’re non polarized high voltage caps with the leads in an axial configuration meaning they have a lead on each end like a resistor. After searching long enough I found them on the Allied Electronics website. I’ve ordered them and should have them all in a couple weeks. Some were on back order.

In my searching I found several good sites about vintage electronic repair:

Antique Radio

Antique Electronic Supply

Just Radios

The last half of this weeks video explains how a phonograph produces sound from a needle in a groove on a record. For a more in depth explanation visit this page:
Record Technology

I hope you enjoy this video and come away with an appreciation for this wonderful old technology that all of us older folks grew up with.

Keep on hackin!

Last year I was given a bunch of vintage electronics and in the pile was a Zenith console stereo from 1960. It actually worked but needed a tune up. I stashed it in our shed for the summer while I worked on other things but now that I seem to be stuck inside due to the cold weather I figured it was time to haul it out and restore it.

After some testing I discovered that a few tubes were in need of replacement. I found the ones I needed on Ebay along with a new phono needle and cartridge.

Follow along now as I take you back in time to 1960.

Enjoy the video and…

keep on hackin!