Gakken EX-System

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The Gakken EX-150 set up for experiment #108.

The Gakken EX-System is a series of educational electronics kits produced by Gakken in the late 1970s. The kits use denshi blocks (also known as electronic blocks) to allow electronics experiments to be performed easily and safely. Over 25 years after its original release, one of the main kits from the series was reissued in Japan in 2002.


A brief timeline:

Gakken and Denshi Block Mfg. Co. Ltd. collaborate to release denshi block kits under Gakken's name.
The EX series was released.
The successor to the EX series, the FX series, is released.
Gakken stops producing denshi block kits.
The EX-150 is reissued in Japan, and is successful enough to justify the production of an expansion kit.

EX-System kits[edit]

Several denshi blocks from the Gakken EX-150.

An EX-System kit consists of:

Denshi blocks[edit]

A denshi block (or electronic block) is a small plastic box containing an electronic component. Each block has conductive metal strips on its sides, and when two blocks are placed side-by-side, their metal strips touch allowing electricity to flow between them. The top of each block is labelled with a schematic representation of the component it contains.

A circuit is built by placing a configuration of denshi blocks in a two dimensional grid. Because of the two dimensional layout and the labels on the blocks, a configuration of blocks resembles a schematic of the circuit.

While most denshi blocks are of a standard size, there are some larger blocks for containing complex components. In particular, the synthesiser block and the FM tuner block are much larger, occupying an area 4x5 standard blocks and 3x6 standard blocks, respectively.

The main unit[edit]

The main unit holds the grid of blocks (it has room for 6×8 standard blocks), batteries and some additional circuitry. When fully expanded, the main unit contains:

External apparatus[edit]

Some circuits require apparatus which are unsuitable for putting inside blocks, for example, a crystal earpiece. These have wires which terminate in flat metal contacts, and they are connected to the circuit by sliding the contacts between the metal strips of two neighbouring blocks.

Some experiments also involve non-electrical apparatus, for example, the optical fibres from the optical experiments kit. The optical fibres are connected via a special block.

Instruction booklet[edit]

The instruction booklet gives the correct arrangement of blocks to make each circuit, a full schematic for it and a brief explanation of how the experiment works.

The original EX-System kits[edit]

The names of the original kits, EX-15, EX-30, etc., give the number of experiments that could be performed with them. By purchasing expansion kits, EX-A, EX-B, etc., any of the kits could be upgraded to support the complete set of 191 experiments. Each expansion kit added new denshi blocks and came with a piece of external apparatus or some circuitry to be installed in the main unit.

Note that the EX-FM kit is compatible with all of the main kits, although some of its experiments require blocks from later kits in the series.

NameAs upgradeSignificant componentsExample experiment
EX-15antenna, crystal earpieceDiode Detector Radio
EX-30EX-15 + EX-Amorse key block, short cablesMorse Code Practice Circuit
EX-60EX-30 + EX-BIC AmplifierI-Diode Detector + IC Radio (Fixed Bias)
EX-100EX-60 + EX-Ctester probesWireless Water Level Warning Device
EX-120EX 100 + EX-Dmicrophone, CdS cellCircuit which Buzzes when Struck by Light
EX-150EX-120 + EX-Eanalogue meterNoise Level Meter
EX-181EX-150 + EX-System Synthesisersynthesiser block, resistance boardSound of Car being Reversed
EX-FMany main kit + EX-FMFM tuner blockFM Receiver with Microphone Mixer

The reissue kits[edit]

The reissued EX-150 kit from 2002 is almost identical to the original EX-150 from the 1970s. Due to differences in the availability of certain components, there are changes in some of the circuitry. A consequence is that some of the experiments have been altered.

Optical expansion kit[edit]

The reissued EX-150 sold well enough to justify an expansion kit. It is designed for the reissued EX-150 only and, allegedly, will not work with the original. The expansion contains components for performing optical experiments, including LED blocks, optical fibres and a 555 timer IC block. As some of the experiments involve two separate circuits, a plastic tray with room for 6 x 5 standard blocks is also provided.

An example experiment:


The EX-System Synthesizer Block.

The sound synthesiser was based around the Texas Instruments SN76477 sound chip. Since the chip requires a separate 9V power supply, the synthesiser block had a compartment for holding a 9V battery.

Although the EX-FM tuner block supported 10 new experiments in Japan, in the English language version available in Europe, only 4 experiments are described.

A Japanese man, Hiroyuki Inoue, built an IPv6 communication module as a block for the EX-150.[1]

The Denshi Block system was also sold under the Skilcraft[2] and Tron Link[3] brands.


The FX-System was introduced in 1981.[4] It used TMS1000 processor.


Dostál, J. Electronic kits in education. Olomouc, EU: Votobia, 2008. 74 s. ISBN 978-80-7220-308-6. --- DEADLINK

External links[edit]