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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:
An EX-System kit consists of:
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 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:
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.
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 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.
|Name||As upgrade||Significant components||Example experiment|
|EX-15||antenna, crystal earpiece||Diode Detector Radio|
|EX-30||EX-15 + EX-A||morse key block, short cables||Morse Code Practice Circuit|
|EX-60||EX-30 + EX-B||IC Amplifier||I-Diode Detector + IC Radio (Fixed Bias)|
|EX-100||EX-60 + EX-C||tester probes||Wireless Water Level Warning Device|
|EX-120||EX 100 + EX-D||microphone, CdS cell||Circuit which Buzzes when Struck by Light|
|EX-150||EX-120 + EX-E||analogue meter||Noise Level Meter|
|EX-181||EX-150 + EX-System Synthesiser||synthesiser block, resistance board||Sound of Car being Reversed|
|EX-FM||any main kit + EX-FM||FM tuner block||FM Receiver with Microphone Mixer|
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.
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: