- Category: Shack Talk
- Published on Tuesday, 28 August 2012 11:00
- Written by David L Norris, KG9AE
Many seem to think that the "Maker" phenomena is a new trend but it's really just a resurgence of how things were before mass production moved out of the US. Most of the time since radio and electricity went mainstream in the late 19th century designing and building your own equipment was the attraction. Back then it was necessary because there was no store which sold such equipment. These days you can go buy anything you'd ever need. When I was a kid in the 1980s pretty much everyone interested in Ham Radio or electronics had built a Heath Kit or Conar or some other piece of gear and almost everyone had built their own antennas. Building something of your own design is a very valuable learning experience and I strongly encourage everyone, ham or not, to build something of their own.
Sometimes building kits was to learn but often it was out of necessity. Kits are often quite inexpensive compared to the prebuilt options and if you are careful and patient and follow the directions they are normally easy to build. Mind you, complex kits may be tedious but good kits will hold your hand through the entire process. Easy to follow and inexpensive kits still exist and have amazing capabilities compared to old school kits. You can find anything from simple meters up to full digital DSP HF-VHF Transceivers comparable to, or better than, any commercial factory-built rig.
The very first piece of electronic gear of any kind that I built was a Heath Kit HM-2102 2 Meter 25W/250W Wattmeter in the late 1980s. It was new in the box and had been sitting around unbuilt for some years. So my uncle gave it to me to try and get me interested in Ham Radio. Well, I was hooked. I immediately started studying for my novice class license. Afterall, I needed a license and a radio now that I had this awesome meter!
Recycle and Share
You can begin your journey into electronics with a kit but you may find yourself needing to provide your own chassis and other hardware to complete the kit. Many kits only provide the basic electrical and electronic components and leave cabinetry and other details to you. This is really the most fun part of it all. Sure, you can go out and buy all the parts you need new from a nice hardware store. But that takes money and I'd bet most of you throw away all kinds of stuff all the time that would be hugely valuable in a homebrew project.
Don't feel like you need to do these things alone. In fact, I suggest you completely avoid doing these things alone. Maybe you feel like it would be a worthy challenge to tackle a project alone. However it is valuable to know how other people would design such a system before diving in head first. If you are lucky you will be able to locate at least one group of people in your local area that is interested in building things, as well. Here are two valuable resources to find like-minded folks in your area:
And always remember the hackerspace motto: Be Excellent to Each Other!
Parts to Scavenge
Regardless whether you are building your own design, building a kit or just providing your own custom chassis for a kit you will need a few things before you begin. You will need tools, some hardware supplies and some electronic components.
- Sheet Metal chassis covers, brackets, shields, etc
- Screws & Nuts (Machine, Sheet Metal, not wood)
- Washers (Metal, Teflon, etc)
- Gears, pulleys, clutches, etc
- Rubber Gaskets, O-Rings, Seals, belts, etc
- Rubber Feet, spacers, shock absorbers, etc
- Brakes (felt, paper, etc) - adds friction to make a knobs more precise\
- Wire, wiring harnesses
- Connectors, plugs, jacks, etc
- Meter movements
- LEDs, lamps, etc that are easy to remove
- Potentiometers, High Power resistors, rotary encoders and other knob-like bits
- Knobs! Plastic knobs to turn potentiometers, inductors, capacitors.
- Heatsinks, Radiators, Heatpipes (chunks of aluminum & copper with fins that conduct heat)
- Electrolytic Capacitors
- Transformers & Power Supplies
- Inductors, magentic coils, anything with enameled copper wire is invaluable.
- LCD Computer/TV Monitors (good bartering material with a TV shop, they usually cost $4-10 to fix if the screen itself is intact. High resell value and low cost to repair.)
Parts to Buy
If you have other scavengers nearby ask them before buying new. Like me, they may have significant stores of NOS (new-old-stock) items they have scavenged from TV/Radio shops, fleamarkets, hoarders, etc. They may be willing to barter with you; I know I will. I have been known to give away parts that are interesting but not particularly valuable. For instance, I have a box of 8088 CPUs which are utterly worthless to sell but they are a brilliant CPU to learn how CPUs work. If nothing else its a good chance to see what types of things others scavenge to give you ideas on how to go about doing so. And, hopefully, they can give you storage ideas to keep the space needed to a minimum. The goal is to have useful parts on hand without spending much money; not to be buried in parts no one will ever use.
- Microcontroller, CPU, RAM, ROM or any other IC Chip (Frys!)
- Resistors (Newark, Digikey) - Buy 100 of each standard value/precision and you're set for years. In bulk you're looking at $30 total for every possible standard resistor. At Radio Shack you're looking at $20 for a pack of 50 with 43 values you'll never use.
- Capacitors (Newark, Digikey) - NOS is best. If you must buy new avoid Korean high-density electrolytics. There is a near 100% chance of failure on high density electrolytics unless you know precisely what you are doing.
- Inductors (Newark, Digikey, specialty shops) - Learn to make your own! Its trivial and cheap. (Enameled copper wire you scavenged above)
- Vacuum Tubes (Buy NOS from scavengers if possible, Russian-made if not.)
- Transistors (Newark, Digikey, Frys)
- Proto-Circuit boards (Frys)
Standard Electronics Components
This is a list of basic electronics components that I keep on hand at all times for experimenting and building simple circuits. I also have a vast number of other devices on hand but I don't replenish those until I need more.
Resistors come in standard values called "preferred numbers" and values are based on a geometrical progression of tolerance. The numbers used in electronics are defined in the IEC60063 E Series and come in divisions of 6, 12, 24, 48, 96, 192. Resistors with a 5% tolerance have values spaced 5% apart. 10% and 20% resistors are fairly unheard of these days but were very common in the first half of the 20th century. So you are likely to find them in salvaged items or older gear. ¼W carbon resistors are sufficient for most circuits. Sometimes you'll need a value not listed in my table and for that you can combine several smaller values at least until you can buy the exact value you need. For example, if you need a 150kΩ then a 100kΩ + 47kΩ is only 2% off the marked value. With a good meter in that situation you can grade the resistors you have on hand and with luck find some closer to your desired value.
Here are the values I keep on hand in bulk quantities. This entire set should cost under $25 to assemble from Digikey or Newark.
As with resistors, capacitors come in IEC60063 E series numbers rated at various voltages, temperatures, polarizations and made of a vast array of materials. Your best bet to start with is to grab an assorted parts kit. Honestly, you will never need all of these values below. Most circuits only use 4 of the E series numbers: 1, 2.2, 4.7 and 6.8 and again the reason for this is tolerance. E6 is 20% tolerance and electrolytics in particular have a typical tolerance of 40%. (What? 40%! Yep. Your 10µF may be 7-15µF.) Which exact values you'll need are entirely dependent of the types of devices you build. When in doubt, remember you can (almost) always combine smaller values effectively. Tolerances on capacitors are pretty loose unless you're dealing directly with RF and usually you can adjust the other nearby components a little to make up for not having an exact value. These tables may also help you select the correct type of capacitor for the function it will be performing.
You probably only need a fraction of these values. My rule of thumb is that if I need a value then I buy in bulk. I like to keep the shipping under 10% of the order price. For example, if I need to buy ten 470µF I'll go ahead and buy 50 of them to hit the price break. 10 might cost $7 where 50 are $18. In the US, you can go with USPS First Class mail (padded envelope) on the shipping for around $1.80 and still get it in 2 days.
There is such an awe inspiring variety of transistors available you could spend forever looking through catalogs. However, for most mundane purposes a few will suffice. You will need to seek out some specialty parts for high power RF amps and odd devices. But for day to day circuits I think this table will serve you well. Most transistor applications are going to use NPN or their equivalent. Sometimes you'll need a complimentary pair; for example, to drive a transformer such as an IF inter-stage amp you should be using complimentary pairs here. These are usually low power situations. The faster the device needs to switch the more likely you are to need more exotic devices like JFETs and MOSFETs.
|2N3055||TO-3||NPN Power, 115W: Audio, Power|
|TIP47,48,49,50||TO-220||NPN Switching, 40W: Power Control|
|2N3904||TO-92||NPN Preamp, 625mW: Audio, RF, Power, Compliments 2N2906|
|2N3906||TO-92||PNP Preamp, 625mW: Audio, RF, Power, Compliments 2N3904|
|MPF102||TO-92||N-Channel JFET RF Amp, 350mW: VHF Preamplifier, IF Interstage, Switching|
|IRF510||TO-220||MOSFET, HEXFET, 50W: High Speed Switch|
I'm not even going to bother listing every single part because it doesn't matter much and its like listing the names of all the stars in the sky. Buy some rectifiers (e.g. 6A, 50V), buy some switching diodes (e.g. 1N914) and I will list the Zeners I keep on hand. Zeners are used for voltage regulation and shunting (shunting: voltage gets too high and you shutdown the circuit; keeps things from exploding and/or catching fire.)
|Part #||Breakdown Volts||Max Current|
This is just a very short list of useful ICs to have on hand. I have a few hundred times more than this but these are a good start.
|LM7805, LM7808, LM7812, LM7815||TO-220||3 pin 5V, 8V, 12V, 15V regulators in a tab mount transistor case.
8V is handy because PLL circuits in radios commonly use them to power the VCO and this is a very common device to fail.
|TL062CP||8-PDIP||8 Pin Operational Amplifier with 1MHz bandwidth 3.5V/µS
Makes a decent Audio or IF pre-amplifier or comparator.
|4N36||6-DIP||6 Pin Optocoupler with Transistor Output 5300V Isolation.
This allows you to electrically-optically isolate the output of one analog device with the input of another analog device. Can be used for digital as well.
|MAX232||16-DIP||16 Pin RS-232 Line Transceiver.
TTL/CMOS IC chips tend to be 5V unbalanced (reference to ground) with no flow control. RS-232 computer serial ports are 12V balanced (referenced to -12V) with various forms of flow control. This chip converts both ways between the two line formats. Most radios need these to talk to a PC.
|NE555, NE556, NE558||8, 14, 16-DIP||8, 14, 16 Pin Single, Dual, or Quad Timer.
Marvelously wonderful and simple timing chip. You can build oscillators and whatnot with these.
8 Pin Phase Locked Loop Tone Decoder.
|7400 series||DIP||TTL ICs that perform all sorts of logic and digital switching functions.
I keep handy 7408, 7474, 7420, 7475, 7402, 7430, 7490, 7404, 7432, 74107, 7405, 7406, 7447, 7446, 74192, 74161 and the list goes on for hours. They are cheap and readily found as salvage. I find huge bags of them at fleamarkets all the time. I have dozens of other kinds, as well. If you have one you can't find I might be able to help.
CMOS ICs that perform various digital logic and analog switching functions.
Just as an example, this inventory from a single storage box of IC chips I have on hand:
|Radio Shack||7555||5||16-pin 555 timer|
|BCFD||1073BC||7||"GTE LABS" Like MC477 Dual 4-in AND gate|
|SCC||4016AE||11||CMOS QUAD BILATERAL SWITCH|
|CD||4016BE||19||CMOS QUAD BILATERAL SWITCH|
|MC1||4016CP||64||CMOS QUAD BILATERAL SWITCH|
|CM||4024AF||67||7-Stage Ripple Carry Binary Counter|
|CD||4043BE||93||CMOS QUAD 3-STATE R/S LATCHES|
|MC||4044P||1||Phase Frequency Detector|
|CD||4051BD||1||Single 8 channel Analog Multiplexer/Demultiplexer|
|CD||4051BE||50||Single 8 channel Analog Multiplexer/Demultiplexer|
|CD||4052BE||31||Dual 4-Channel Analog Multiplexer/Demultiplexer|
|CD||4066BE||30||CMOS QUAD BILATERAL SWITCH|
|CD||4066BEX||36||CMOS QUAD BILATERAL SWITCH|
|MC1||4515AL||2||4-Bit Transparent Latch/4-to-16 Line Decoder|
|MC1||4515CL||2||4-Bit Transparent Latch/4-to-16 Line Decoder|
|MC1||4584B||4||Hex Schmitt Trigger|
|MCM||6810LD||5||128 Bytes x 8-bit RAM|
|SN||74154J/N||21||4-to-16 Line Decoder|
|SN||7430N||18||8-INPUT POSITIVE-NAND GATES|
|SN||7442AN||9||4-LINE BCD TO 10-LINE DECIMAL DECODERS|
|SN||7474N||10||DUAL D-TYPE POSITIVE-EDGE-TRIGGERED FLIP-FLOPS WITH PRESET AND CLEAR|
|74LS00N||2||"Controller for Timex 1000" parts bag|
|74LS30N||2||"Controller for Timex 1000" parts bag|
|74LS32N||2||"Controller for Timex 1000" parts bag|
|Intel||P8048||3||Microcontroller (Intel MCS48 series)|
|Intel||P8255A||16||CMOS Programmable Peripheral Interface|
|Misc.||P82C55A||4||CMOS Programmable Peripheral Interface|
My list is not exhaustive. I could type until the end of time and not cover half the things you might need. I am utterly amazed all the time at the vast variety of things I've come across over the years. Most people look at a device and see only the thin veil of the outside. Me, I see through it for what it is: A big pile of parts that is eventually going to be obsolete.