Electronic project kits: hands on with a vintage 160-in-1

In this day and age with the bewildering availability of electronics readily available, deciding on a project to embark on can be paralyzing. This sentiment was best summed up recently in this Hacker News comment on an article announcing the CHIP Pro:

I have the chip, esp8266, rpi, teensies, trinkets, arduinos… I studied electronics principles and built various circuits.. yet I have no idea what I can practically use these devices for in my life. They all sit in a box and I have a hard time justifying buying more of them.

See also: the paradox of choice, analysis paralysis, etc. Decades ago, all-in-one electronic project kits were popular. Shown above is the Science Fair 160-in-1 Electronic Project Kit, #28–258 (image source: eBay), © 1982.

With a modest number of components, 160 projects could easily be built by inserting wires into the spring terminals connected to each component. An included manual guided you through each of the projects, introducing new concepts and providing structure, while still offering some latitude of freedom to tinker — but, crucially, not the nearly-infinite amount of latitude available on modern electronic marketplaces today. You are constrained by the components in the kit (unless you add your own), and the included project documentation (unless you invent your own), a finite possibility.

I was always a fan of these #-in-1 project kits for this reason, and learned a lot playing with them in the past. Sure, I tinkered with the Raspberry Pi and Pi Zero, and have ordered an ESP8266 I’m looking forward to as well, but there was something about the 1980’s kits (this was also during the heydey of Heathkit, 1947–1992) which I feel may have not been captured in today’s modern hobbyist popular electronics. Perhaps it is nostalgia for a simpler time, granted I wouldn’t want to go back to then and miss out on the vast availability of diverse cheap electronics today (thank you, Aliexpress and especially Shenzhen: The Silicon Valley of Hardware), but I think it can be instructive to take a look back and see what we can learn from 1982.

A brief tour of electronic project kit models

Another view of the 160 showing the box, manual, and accessories (eBay):

Radio Shack 300-in-1 Electronic Project Lab, #28–270 (eBay):

Fun with Electronics Electronic Workbench, 25-in-1. This kit came with the cardboard unpopulated (eBay), and you assembled the components:

The manual was published in 1994 by Andrew McMeel Publishing, ISBN 978–0836242317

There were other kits as well, Science Fair 200-in-1 #28–249 (eBay) from 1981, an expanded version of the 160-in-1:

and its predecessor, Science Fair 150-in-1 #28–248 (eBay), 1976, ~the 160:

or the Elenco MX-908 300-in-1 (eBay), same components as the Radio Shack model but a different color scheme:

There were a variety of other project kits from Science Fair / RadioShack:

  • 10-in-1 (#28–225)
  • 20-in-1 (#28–245)
  • 25-in-1 (#28–226)
  • 30-in-1 (#28–175)
  • 40-in-1 Electro-magnetic (#28–252)
  • 50-in-1 (#28–227)
  • 60-in-1 (#28–261)
  • AM/FM Radio (#28–234)
  • 65-in-1
  • Solar Power (#28–246)
  • 75-in-1 (#28–247, #28–267)
  • 100-in-1
  • 130-in-1 (#28–259)
  • 150-in-1 (#28–248)
  • Communications (#28–254)
  • 160-in-1 (#28–258)
  • 200-in-1 (#28–249, #28–265)
  • Microcomputer (#28–260)
  • Digital Voice (#28–264)
  • 300-in-1 (#28–270)

This list was compiled by searching for “science fair 38-###” so it may be incomplete.

Searching for manuals

The Philips EE electronic experiment kits are well preserved at http://ee.old.no/. But what about the Science Fair kits? There is a thread at All About Circuits. Science Fair 200-in-1 manual Science Fair 200-In-One Manual.pdf at Sendspace (Dropbox). Supposedly the old Radio Shack site had them:

The part numbers you’re looking for are
280080_p1_pm_en.pdf and for the second book substitute a p2 for the p1.
I have the files on my pc but they are corrupt, they are about 6 or 7 mb each. The date on these is 2000.

but I can find this “280080_p1_pm_en.pdf” file nowhere, the only reference on the web is on the All About Circuits website. Nelly20a14 posted some photos (archive) but they appear to be heavily cropped and incomplete. This RadioShack link for 300-in-1 is still alive, but owner’s manual is unavailable. Also the RadioShack 160-in-1, only including the detailed parts list and list of projects.

Then I found this excellent site, with the most comprehensive information:

including the complete 160-in-1 manual! (Dropbox mirror)

Where did this manual PDF come from? Tracked it down to: FET Tricks: The Early Days — Science Fair 150-in-One Kit, Shane Trent’s blog:

I wanted to share the manual so I went about scanning and converting to pdf. To facilitate scanning, I took the manual to a local copy shop had them trim the spine from the manual using a stack paper trimmer, I believe charged me $0.50 for the service. Then it was mostly just feeding a small stack of pages at a time into my Fujitsu Scansnap S300 scanner. I scanned the pages in black and white but wanted color for the cover which required combining two pdf files. But most of the effort required was addressing the odd double feed which caused skipped pages. I believe it turned out well. Below is the resulting manual in pdf format.
Science Fair 160-in-One Electronic Project Kit Manual

This is the same file (RadioShack 160 in One Electronic Project Kit.pdf = 160_manual.pdf), both 28427667 bytes and MD5 hash a505facd1a315038cff7f621d21c945a. Many thanks to Shane for bringing this excellent manual into the digital realm.

First circuit with the 160-in-1 kit: a pulse oscillator

The 160-in-1 can be acquired inexpensively secondhand, e.g. off of Craigslist. Mine didn’t come with:

  • the manual (but I found it online, see above)
  • the morse code key (but it’s just a momentary switch, no big loss)
  • the earphones (TODO: acquire a replacement)
  • the special light shield for the cadmium sulfate cell (oh well)

but was otherwise complete and in good condition.

However there was a slight problem with the 9V battery clip. The female connector did not clasp tightly, and the female on the battery side was too tight. Nothing a pair of pliers can’t fix:

Now that the power is connected working (used a fresh 9V battery), I proceeded to wire up the first circuit, starting with “4. Machine Gun Pulse Oscillator” just for fun:

Wiring it up (without the morse code key):

And it works perfectly! The speaker is louder than I remember it, maybe because of the fresh 9V batteries. The circuit also runs well off of 3V.

Now for a closer look at this kits.

Kit components

What are these kit made of? Their constituent components are surprisingly similar between each kit. In fact, one could probably easily rebuild a very similar kit from scratch using common off-the-shelf components. I considered this, making the circuits from the manuals using what I had on hand, but also decided to pick up this kit to ensure I have the exact parts needed.

The detailed parts list can be found after all these years at http://support.radioshack.com/support_games/doc22/22608.htm:

280-0258       160-1 LAB                             Faxback Doc. # 22608

To order parts call 1-800-843-7422 or visit your local RadioShack store.

Reference # Cat.No. Description NP Part #
------------------------------------------------------------------------
11318524 DIODE 1N4001 RECT 600V SI 1N4001
11319340 REPLACED BY DX-0162 1N60
11319373 1N60P
11329794 REPLACED BY 2TR0158 2SA733
10519239 REPLACED BY 2TR0698 2SC945
2TR0698
W/5 LEADS A0291
10539260 ANTENNA,BAR ASSY A0304
BATTERY HOLDER FOR 2AA PE B0166
CLIP,BATTERY B0172
USE JE0213 B0209
11449808 BA306 ANALOG SW BA306
10556264 CAP TUNING C4242
REPLACED BY A0304 CA0619
REPLACED BY CC101JJBCB CC101JJBC
10571776 PKG OF 5 CC101JJBCB
REPLACED BY CC102JJBCB CC102JJBC
10571826 PKG OF 5 CC102JJBCB
10571958 PKG OF 10 CC103JJBCC
10572196 PKG OF 5 CC104JJBCB
10572451 10UF +-20 16V ALP CC106MDCA
10572550 PKG OF 5 CC107KCBAB
PIPE CDS CS0028
10586188 CELL SOLAR MSC-0753 CS0099
CELL CDS KS85S CS0100
10637379 EARPHONE E0007
HOLDER BAR ANTENNA H1535
SOCKET SIGNAL LAMP HB0535
TERMINAL,SPRING,BAG OF 10 HB4804
BLUE HC1709
LEVER KEY HC1710
10740520 STORE STOCK UNDER 270-324 JE0213
KNOB FOR TUNING CAPACITOR K0669
KNOB VAR RES K5073
MORSE CODE K5074
10794295 LAMP RED L0541
LED 7 SEGMENT L0739
METER M0294
10852291 MANUAL USERS 28-258 MU2800258
BA302 AMP MX3039
10940187 100 5% 1/4W CBF RES N0132EEC
10941029 470 5% 1/4W CBF RES N0169EEC
10941342 1K 5% 1/4W CBF RES N0196EEC
10941680 2.2K 5% 1/4W CBF RES N0216EEC
10942118 4.7K 5% 1/4W CBF RES N0247EEC
10942498 10K 5% 1/4W CBF RES N0281EEC
10942985 22K 5% 1/4W CBF RES N0311EEC
REPLACED BY N0340EECC N0340EEC
10943249 PKG OF 10 N0340EECC
10943611 100K 5% 1/4W CBF RES N0371EEC
220K 5% 1/4W CBF RES N0396EEC
RES CAR F 360K 5% 1/4W N0412EEC
470K 5% .25W CBF N0423EEC
10971364 POT VARIABLE P1656
10985802 RELAY 225 OHM 9V R8158
SWITCH SLIDE S2241
SPEAKER REMOTE S4565
11106069 TRANSFORMER INPUT TD0097
11106077 TRANSFORMER OUTPUT TD0136
CORD,ANTENNA W1587
11114923 BLACK-380MM W3320
BLANK,PCB FOR LED X7159
BOX WOOD Z3245
PANEL FRONT PLASTIC Z6408

(This list was generated on 07/08/2005)

And 160_part_list.pdf from zpag.net, accompanying the manual:

Breaking it down:

Passives

  • Resistors: 100, 470, 1 k, 2.2 k, 4.7 k, 10 k (2), 22 k, 47 k, 100 k, 220 k, 470 k, each 5% 1/4W carbon
  • Capacitors, ceramic: 10 pF, 100 pF, 0.001 µF, 0.01 µF, 0.02 µF, 0.05 µF (2), 0.1 µF
  • Capacitors, electrolytic: 3.3 µF, 10 µF, 100 µF, 470 µF

Semiconductors

  • PNP transistors: 2SA733 small signal (2), pinout: ECB, obsolete as of 23-Feb-2012, “replaced by 2TR0158”
  • NPN transistor: 2SC949, pinout: ECB, “replaced by 2TR0698”

The resistors and capacitors are nothing special, and the diodes appear fairly ordinary, but the transistors require more explanation.

There are two types of bipolar junction transistors in the 160-in-1:

image credit: Jeff Keyzer via Flickr, slightly cropped

NPN is more common (or is it?), but for some reason they included two PNPs and one NPN. The PNPs are 2SA733, the NPN is 2SC949, and both have a pinout of emitter-collector-base. What could be suitable modern replacements? Both are general-purpose (2SA733: for general-purpose amplifiers, “collector currents up to 300 mA”; 2SC945: low-speed switching and “use in driver-stage of AF [audio frequency] amplifiers”). The RadioShack website recommends 2TR0158 and 2TR0698 as replacements, respectively, but these appear to be RadioShack’s own internal part numbers, not much information available on them.

Fortunately I had a handful of miscellaneous transistors from my junk box to try out. This circuit can serve as sort of a transistor-checker, but only for PNP transistors with ECB (or EBC?) pinout. Wired up to a breadboard and tested:

Working PNP transistors:

  • 2N4403 general-purpose PNP transistor (EBC) (2)
  • MPS A56 PNP general-purpose amplifier (obsolete 2012) (2)
  • KN3906 general-purpose PNP transistor (EBC) (2N3906) (2)

TODO: also test NPN, with other circuits

None of these transistors I had were compatible: (or, they may not actually be transistors but other integrated circuits in similar packages?):

  • C202IQ H, 115 76F, WF5172, T K1118 4L
  • C3204 Y, C2236 Y 7B, A1015GR PH39

Integrated Circuit: audio amplifier

According to the zpag Électronique/Electronic Kit website, this is the BA306 NTE1431 Audio Driver. Comes in a SIP-7 package:

In the 160-in-1, capacitors are added:

  • 0.02 µF ceramic between 94–95 (7–6) = Vcc and Output
  • 3.3 µF electrolytic between 96–97 (3–4) = Bypass and GND

There may be an error in either the above schematic or datasheet: pin #5 is N.C. = not connected, but shown as connecting to the base of Q2 in the schematic, also to the collector of Q1. Either way, it isn’t broken out in the 160-in-1 project kit board.

This IC is used as an amplifier:

  • 82. Vox-Voice Operated (Transmit) Relay
  • 142. I.C. VU Meter
  • 131. I.C. Radio

or an oscillator:

  • 102. Light Controlled Burglar Alarm
  • 105. CdS Controlled I.C. Oscillator
  • 115. I.C. Morse Code Practice Oscillator
  • 153. I.C. Oscillator/Component Tester

The schematics show the IC with an amplifier symbol, similar to an opamp but not with extremely-high gain, it can be used without feedback, as seen in the I.C. Radio:

This particular IC is not too interesting in modern times, it is fairly obscure, and many other amplifiers are available instead. Can the IC in these circuits replaced with opamps in a closed loop configuration?

With a non-inverting opamp: Vout = Vin*(1 + Rf/Rg).

Opamp chips: 741 (popular but there is newer), LM324N quad operational amplifier (which I had salvaged from an UPS).

TODO: test LM324N replacement in these circuits

Knobs: Control and Tuning

“Control” is a potentiometer conveniently located near the speaker, useful for volume or frequency adjustments. Specified as a 50 kΩ variable resistor in the parts list, I measured 43.38 kΩ across the two resistor terminals. Rough measurements adjusting the wiper to each digit:

  • 0: 45 Ω
  • 1: 160 Ω
  • 2: 5.4 kΩ
  • 3: 10 kΩ
  • 4: 17 kΩ
  • 5: 24 kΩ
  • 6: 31 kΩ
  • 7: 36 kΩ
  • 8: 40.04 kΩ
  • 9: 43.55 kΩ
  • 10: 43.39 kΩ

Curious how the resistance barely varies from 9 to 10, maybe by design or an artifact of old age.

“Tuning” is an unlabeled variable capacitor in radio circuits:

specified as 265 pF in the parts list, I measured… 0–1 nF, and ∞ Ω. Broken?

This may be a possible replacement: Fudan brand single joint air medium variable capacitor 12–365PF. TODO: test a circuit using the variable cap

Speakers

The speaker is one of the most important components of this kit. It provides an essential output: auditory feedback to the listener who built the circuit. I still think of low-capacity ceramic capacitors as “high-pitch”, due to the tone heard from this speaker when used in an oscillator.

It is always connected to the output transformer (except in “103. Relay and Speaker Buzzer” where the relay is used to generate an AC waveform instead), although the output transformer is sometimes used by itself.

A good opportunity to test some old speakers I had around, using the same machine gun oscillator circuit:

The speaker is only specified as “57 mm S-4565” in the parts list, but I measured 8.2 Ω, which looks about right. The three extra speakers shown above were all labeled 8 Ω, and worked just fine in this circuit.

There’s also a set of earphones, listed as “Earphone, high Z crystal type (no DC path) E-0007”, could be useful sadly no longer present in this kit I own.

TODO: can one use cellphone/computer headphones as an alternative?

Transformers

Two small transformers:

  • Input transformer (yellow), TD-0097 / 11106069
  • Output transformer (red), TD-0136 / 11106077

These part numbers appear to be kit-specific, couldn’t find much information. However, Wikipedia: Transformer types has some info:

Audio transformers are specifically designed for use in audio circuits to carry audio signal. They can be used to block radio frequency interference or the DC component of an audio signal, to split or combine audio signals, or to provide impedance matching between high and low impedance circuits, such as between a high impedance tube (valve) amplifier output and a low impedance loudspeaker.

Taking some measurements on the red (output) audio transformer:

  • 1.3 Ω secondary coil (output, connects to speaker)
  • 56 Ω primary coil (input, connects to circuit)
  • 28 Ω from center tap on primary coil to either side

Comes to an estimated 56/1.3 = 43:1 ratio.

And on the yellow (input) transformer:

  • 156.3 Ω on secondary coil
  • 190.9 Ω on primary coil
  • ~96.1 Ω from center tap

The input transformer comes to an estimated 1.2:1 turns ratio, much lower.

Measuring the AC voltage on the output transformer secondary coil, when producing sound using the machine gun pulse oscillator project, it reads in the hundreds of millivolts, and AC current in the tens of milliamps. Input voltage on the other hand reads from several volts to about ten volts. The purpose of this output transformer is now clear: transform high voltage / low current into low voltage / high current to drive the speaker.

How could we find a suitable replacement transformer? Here’s what I have:

The biggest transformer is from a microwave oven, next biggest from an UPS, the rest from various sources long lost to time. But what’s important here is the turns ratio. We want ~40x more turns on the primary coil (with a center tap) than on the secondary, or at least enough to drive the speaker.

Most of the transformers I had either possessed a low ratio (including 1.0, for isolation transformers) or lacked a center tap. The lower ratio transformers may be useful for replacing 160-in-1’s “input transformer”. For the output transformer, I found one suitable:

  • primary 61.5 Ω, secondary 0.8 Ω, ratio = 76:1

This is the small yellow transformer in the bottom with five leads coming out of it (the leads are small stranded wires, giving it away this is for audio). Wired it up into the circuit, and it works fine:

Switches

On the main board, there is a sliding double-pole double-throw (DPDT) switch. The kit also comes with a morse key, simply a momentary switch with morse code printed on the base, but my second-hand kit was missing this. Here’s a picture from the manual instead:

Lights

The lamp is listed as “Lamp, red 2.5 volt, 300 mA L-0541”, but it shines well on 3 volts (2xAA), shown here (the manual warns it will burn out if powered with 9V). Brighter than I expected, and it hasn’t burnt out after all these years, or maybe it has and was replaced by previous owners of this kit. Measured resistance across the lamp of 2.5 Ω.

There is another set of lights on this kit, the LED Digital Display:

Thanks to Jeff Keyzer for this photo (from Flickr, used with attribution, cropped), who either has a better camera or cleaner kit than mine. Close up with each segment illuminated, in low light:

This segmented display is common cathode (negative terminal), here powered by the 3 volt battery power. Listed as:

Light Emitting Diode Display (1.6 V min, per segment, 25 mA max. DC current per segment, 3V max. reverse voltage) L-0541

The hardwired resistors are 360 Ω, assembled on “Printed Circuit Board for LED Display X-7159”. See more about my experiences with segmented LED displays in Emerson MW8675W microwave oven teardown: salvaging the LED display if you are interested. Nowadays LEDs are commonplace, and the newer kits like the 300-in-1 or even newer like various Raspberry Pi kits (as I used in Interrupt-driven I/O on Raspberry Pi 3 with LEDs and pushbuttons: rising/falling edge-detection using RPi.GPIO) include a multitude of LEDs, but this kit only had an incandescent lamp and this modest 7-segment LED display.

TODO: can the left decimal point be powered?

Relay

The electromagnetic relay runs on 9 volts and has a 225 Ω coil (R-8158). It is of the common single-pole double-throw (SPDT) variety, with two leads for the coil, and three contacts: normally-closed, common, and normally-open. This is a good relay, the relays I salvaged in Building an H-Bridge from a salvaged Uninterruptible Power Supply were all SPST, so I had to use four instead of two. Of course, this puny relay is not rated for 220V on the contacts, unlike those in the UPS.

There are more modern components for switching (= the transistor) but the relay remains an easy to understand instructive simple component for understanding switching circuit operation and has some other benefits. 37 of the 160 projects use the relay, from the very first (1. Electronic Candle) to logic circuits (54. Logic “NOR” Circuit, and others) and even high voltage generators (43. High Voltage Generator, and 44. High Voltage Generator II). I tested pressing a 9V battery up against its coil, and it still works, producing a satisfying click.

Antenna coil

Speaking of coils, there is another coil in the “radio circuits” section:

it is only listed as “antenna coil (with 5 leads) CA-0619”, couldn’t find much information about it except it has a solid ferrite core. It may be damaged and needs testing in a radio circuit. TODO: measure inductance, LCR meter

TODO: feasible to wind my own antenna coil using the wire salvaged from Opening a Winsson 62–1225 Power Transformer?

Meter

0–250 µA, 650 Ω movement (“Blue scale is proportional to meter current. Black is logging reference.”) Analog meters have largely since fallen out of favor with the advent of digital displays (7-segment or otherwise). This one included in the kit is for microamps, I happen to have another one for amps:

but have yet to find a practical use for it.

CdS Cell and Solar Cell

image credit: Jeff Keyzer via Flickr

The CdS Cadmium Sulfide Cell photoresistor (KC-4S, CS-0100) is a light sensor. It comes with a thumble-shaped “light shield” (missing):

Similar components are available such as from Adafruit: Photo cell CdS photoresistor. Photoresistors change their resistance based on light levels, but there are alternatives to sensing light such as the photodiode which converts light to current, as I used in SPI interfacing experiments: EEPROMs, Bus Pirate, ADC/OPT101 with Raspberry Pi.

“Solar Cell, open voltage 2.5V typical, short circuit current 29 µA typical at 300 lux” is how the parts list describes the solar cell. A handful of circuits in this kit can be powered entirely off of solar. For those that can’t:

Batteries

A standard 9V battery clip and 2xAA battery holder for 3V. Not that battery-powered circuits are unheard, but modern hobbyists often use AC mains for power these days, often 5 volts through a USB adapter. But all the circuits in this kit can be powered by either of these batteries (some by both), except for “20. Coin Battery” and related projects which itself are about creating a battery from galvanized metal and a cent:

Wires

That’s all for the components, excluding uninteresting construction parts, now to hook them up:

  • 125 spring terminals (HB-4804)

The manual refers to the board as a “breadboard”, technically accurate and originally literally referred to a polish piece of wood used for slicing bread, but this term now almost universally refers to through-hole breadboards (for other circuit construction techniques: Notes on prototyping circuit boards: breadboards, perfboards, and beyond), usually a grid of 0.1" tie points. Modern breadboards still have spring clips, but hidden underneath.

Wires (part number W-1587):

  • 11 white, 7.5 cm
  • 14 red, 15 cm
  • 8 blue, 25 cm
  • 7 yellow, 35 cm
  • 2 black, 38 cm
  • 2 green, 3 m (antenna wire)

The original wires are all stranded and precut, for resilience and repeated insertion into the spring terminals. This kit has many of the original wires, such as these white wires, handy for connecting two adjacent terminals:

but there were also a handful of solid core wires, oxidized. Through-hole breadboards work best with solid core wire (preferably precut to precise 0.1" multiple lengths, as seen in Upgrading to a giant breadboard for Raspberry Pi GPIO peripherals), but this spring-terminal based breadboard works best with stranded wire. It is not ideal because the springs may bend the connectors, but premium jumper wire works in a pinch.

Freeing the Electronic Woodpecker

To wrap up, I’ll build one of the circuits from this kit and then reconstruct it outside of the kit. This is encouraged in the manual:

How times have changed, instead of visiting a local RadioShack or other store for components, one often orders online from overseas.

Anyways, I’ve decided on building the famous electronic woodpecker:

Wiring it up on the 160-in-1 kit (except substituting my own speaker, audio output transformer, and PNP transistor):

Slowly I replaced each component from the kit with one of my own. The Electronic Woodpecker circuit can now be removed from the kit:

…well, almost. Not completely successful in liberating the Electronic Woodpecker. I had no replacement for the 0.05 µF ceramic capacitor (= 50 nF), closest was 0.1 µF (labeled “104"). Didn’t have a AA battery clip so I soldered directly onto two AAA batteries, pretty sure this is not the best technique for several reasons, but it worked. The capacitor from the 160-in-1 kit should also be easily replaceable, I’ve ordered a capacitor assortment (2 pF — 0.1 µF) kit but it’ll be a while before it arrives. Update: received the cap assortment in 11 days. Small components in plastic baggies, I labeled them:

then used a 473 (= 47 nF) ceramic capacitor to finish the circuit, finally completely standalone at last. Broke out the speaker and output transformer on its own circuit board as well, independent from the project kit:


This is only a rough prototype on a mini breadboard, this build could further be improved by moving to a perforated printed circuit board, and permanently soldering the components. And then by assembling it in a case.

However, other circuits may be more useful to rebuild permanently for standalone usage. The various oscillators could serve as a function generator (sine: 148, 149, 150, square: 72, 157, sawtooth: 159, etc.), or the various radio circuits for a portable radio receiver (117–124) or transmitter (125–129).