EX-150 Optics Expansion Pack Circuits

I’m going to take the same approach with the circuits listed in the EX-150 Optics Expansion 60 Pack as I did with the Denshi mini kit, but I’m going to run them as a blog entry rather than as a page off the top menu (because they’ll probably be less useful to readers here). First, some ground work. The Optics Pack includes 30 more blocks, many of which are just simple connector wires, and a few more resistors and capacitors. Additionally, there’s one more transistor and another diode, plus one red and one green LED. The really new parts are a Schottky diode, a photo-transistor, a 50 K-ohm potentiometer (AKA – a pot.), a melody chip, a single-pole double-throw (SPDT) relay, a 3V DC motor and the 555 timer chip. The majority of the parts used for the 60 circuits given in the expansion manual come from the EX-150 kit. If you have the Denshi mini, this is generally not a problem, as there is a lot of overlap.

(Image from the Otona no Kagaku site. Used here for review purposes only.)

However, the EX-150 does have two components built into the case that aren’t in the Denshi that are required for a few of the experiments – a DC current meter, and a photo-resistor (called the CDS cadmium cell). The meter lets you visually measure small changes in current or voltage caused by an input, and the CDS lets you make some light-sensitive circuits (arguably, you can replace the CDS with the phototransistor, but that’s actually a different circuit given later in the book). The Denshi mini also lacks the push button switch block and a couple weird wiring blocks that come with the EX-150, but generally you can work around those by using the paddle jumper wires.

As mentioned in the main review, the EX-150 box is 8 blocks x 6 blocks, while the Denshi mini is 5×5. The expansion pack box is 5×6, but it’s generally used in conjunction with the EX-150 as either overflow, or to create two separate halves of an experiment, such as with a transmitter and a receiver. So, there will be some experiments that you can’t make because they don’t fit into the Denshi mini, but this rare. The expansion pack box doesn’t have power contacts built in, so you can put blocks in place as you like without worrying about destroying a transistor or diode. There’s a 2-cell AA battery holder that clips on to one side of the box, and the paddle jumpers are used to run power to the circuit. Meaning that whatever goes into the EX-150 is at 6 volts, what’s in the Denshi mini is at 4.5 volts, and whatever is powered by the expansion box is at 3 volts. As long as you have a common ground between boxes, it’s ok (and is actually part of the experiment explanations). (Note also that all of the circuits built in the EX-150 box will also run at 4.5V in the Denshi mini box.)

Circuit list:

1) Turning a red LED on and off with a push button switch
2) Measuring current flow through the LED using the pot. and the meter
3) Turning a red LED on and off with a transistor and push button switch
4) Turning on the red LED from the tri-color LED device
5) Turning on the green LED from the tri-color LED device
6) Turning on the blue LED from the tri-color LED device
7) Turning on the red and blue LEDs from the tri-color LED device
8) Turning on the red and green LEDs from the tri-color LED device
9) Turning on the blue and green LEDs from the tri-color LED device
10) Turning on all three LEDs from the tri-color LED device

11) Microphone illumination
Creates a 3-transistor audio amp to let you drive the green and red LEDs from the microphone.

12) multi-vibrator with 1 LED
A flip-flop oscillator that blinks the red LED.

13) One-shot flip-flop driving the red LED
14) Same as circuit 13, but adding the green LED for a 2-state output.

15) Sound switch
1-transistor amp driving the one-shot flip-flop to turn the red LED on when sound to the microphone hits a particular level.

16) 555 Timer
Using the 555 chip and a switch, briefly turn on the red LED.

17) 555 Oscillator
Using the 555 chip, make the red LED blink on and off at a fixed rate, with a 50% duty cycle.

18) Same as #17, but adding the green LED to make a fixed rate railroad flasher. I’m surprised that Gakken didn’t modify this circuit to use the 50K pot to vary to blink rate. Would have made for a much more interesting circuit than the one they actually used.

19) 555 analog flip-flop
Using the 555, the meter and the pot. vary the pot. to see at what threshold voltage the 555 will change state at.

20) Same as #19, but with the LED from Vout to gnd, instead of Vcc to Vout.

21) #17, but with the pot. to vary blink speed

22) Same as #17, but using an output transistor to drive the tri-state LED.

23) Same as #22 but with 2 colors (Green fixed, red blinking)

24) Same as #23, but with red fixed and blue blinking

25) Same as #23, but green fixed and blue blinking

26) Same as #23, but with blue fixed and red blinking
Note that while circuits 23 to 26 are essentially identical, the positioning of the LED terminals on the front or sides of the tri-state block requires a completely different block layout for each within the mounting box. So, rather than teaching electronics, these circuits are demonstrating layout constraints.

27) #17 with a 2-transistor output to drive all three colors of the tri-state LED

28) A variation on #22 to get pink

29) Another variation on #28

30) A variation on #21, with 2 transistors to get 2 new colors

31) A variation on #28

32) Playing the melody chip
The melody chip is like the ones used in musical greeting cards. It’s got about 60 seconds of play time, but only one song. The power pin is connected to Vcc through the push button switch block, and the output is directed to the speaker amp contact of the EX-150 (or Denshi mini) box.

33) Same as #32, but moving the switch position

34) Same as #32, but using a transistor to turn the chip on

35) Same as #33, but connecting the EX-150 CDS photo-resistor to the transistor to make it light sensitive

36) Same as #35, but moving the CDS position

37) Same as #35, but adding the 555 as a light-sensitive one-shot trigger

38) Relay with LED: Connecting an LED to the NC (normally closed) contact of the relay

39) Relay with LED: Connecting an LED to the NO (normally open) contact of the relay

40) Combining #38 & #39: 2 LEDs on the relay

41) Remote driving of the DC motor
A transistor connected to a switch in the EX-150 box (6V) is used to turn on the motor in the expansion box (3V) using jumper wires for box-to-box connections.

42) 2-transistor one-shot timer driving a relay to activate the red and green LEDs

43) Signal lamp
The red LED is connected to the Schottky diode in a closed loop. According to the experiment description, energy from your cell phone antenna can be detected by the Schottky to illuminate the LED. Didn’t work with my cell phone.

44) Wave meter
Similar to #43, but with the Schottky connected to the EX-150 antenna and the current meter, to visually indicate signal strength from your cell phone.

45) Cell phone illumination
Using the Schottky to drive a 2-transistor signal amplifier with the outputs connected to the tri-state LED. Signal from your cell phone causes the LEDs to turn on and off.

46) Fiber Optics circuit
An LED placed in one box is detected by the fiber optic cable connected to the photo-transistor in the other box to make a second LED turn on and off. As you wave the cable near the one LED, the other fades in and out. This is the first real experiment showing how fiber optics work.

47) Variation on #46, turning the DC motor on and off instead of an LED

48) Variation on #46, but with the melody chip

49) Fiber optic voice transmitter
The microphone amplifier circuit placed in the expansion box drives the red LED. The fiber cable is connected to the photo-transistor, which then drives the EX-150 speaker amp. The receiver side works really well, but the microphone side gain is set too low for the Denshi mini mike. I have to yell into the mike for it to have an effect on LED intensity. To make this experiment work better, either a different mike is needed, or a stronger amplifier.  I did jumper to the mike of my webcam headset and the output level of the amplifier did increase a lot, but that introduced a new problem – clipping. Actually, the transmitter LED is normally full-off, so when it does turn on, it’s only transmitting half of the AC audio signal, leading to a lot of distortion at the receiver side.  The amp circuit needs to be modified so that the LED driver transistor is normally at the 50% on point.

50) Fiber optic sound sensor
Like #49, but with the photo-transistor connected to the 555 as a one-shot to turn on the melody chip when the sound strength reaches a specific level. This circuit uses a 560K-ohm resistor from the EX-150 kit, that is not in the Denshi mini, to set the threshold voltage on the 555 chip. The resistors I do have available either make the 555 too sensitive, or not enough.

51) Fiber optic spot meter
The photo-transistor uses one output transistor to drive the meter. You place the end of the fiber cable over a patterned piece of paper, and as you move the cable over the paper, the meter fluctuates with changes in patterns. You can change this circuit to drive one of the LEDs for the same effect.

52) Same as #50, but with the cable removed from the photo-transistor
The PT detects ambient light in the room to play the melody chip.

53) Fiber optic disk player
The expansion pack runs the DC motor, which spins one of the patterned paper disks that comes with the kit. The fiber cable is held over the disk, and the changes in reflected ambient light from the disk are played as high-pitched tones by the EX-150 box speaker amp. The motor runs fast, so I suggest putting the 50K pot. in series with the motor to slow it down a little. If you have stiff cardboard, you can make your own patterns.

54) Same as #53, but with the output of the photo-transistor is connected to the 555 one-shot trigger to drive an LED.

55) Just the DC motor spinning the pattern disks

56) Metal detector
A simple oscillator using the 4mH coil as an an input. The closer a piece of iron or steel is to the coil, the higher the pitch of the tone from the speaker amp. A separate circuit causes an LED to also light up. Uses too many parts from the EX-150, and can’t be built with just what’s in the Denshi mini.

57) Traffic Light
This is a two-parter, with the 555 timer used to turn the relay on and off. The relay activates the red and blue portions of the tri-state LED. Jumpers to the expansion box connect the red LED line from the EX-150 to the input of a timer flip-flop. The output of the flip-flop then returns to the EX-150 to activate the green LED. The result is that what you see is blue, yellow, red (in Japan, blue and green are both referred to as “blue”). Too big to fit in the Denshi mini case.

58) Ambulance siren
The 555 in the expansion box sets up the timing for a 2-tone oscillator through the relay. The relay then acts as a switch to the oscillator in the EX-150 that outputs to the speaker amp. Uses the center-tap transformer from the EX-150 kit (not supplied with the Denshi mini).

59) Police siren
Same basic idea as #38, but with the 555 connected to a transistor instead of the relay. Also uses the center-tap transformer.

60) Radio tuning indicator
The EX-150 is used to set up a simple 3-transistor AM radio. The output signal is then jumpered to the 555 set up as a threshold sensor in the expansion box. When the level is below the threshold, the green LED stays on. When a station is detected, the red LED activates.


Of all the circuits in this manual, the ones I can’t build right now are those using the CDS photo-resistor, the meter, and the center-tap transformer. Plus there are a couple that use oddball resistor values (560 Kohms) or wiring blocks that aren’t supplied with the Denshi mini. This represents around 15 circuits, total that I can’t build using just the Denshi mini.

I’ve always liked the 555, so I’m happy being able to play with the variable-rate 555 LED blinker.

I like the circuits using the fiber optics components. My favorites are the 2-LED and tri-state LED flashers, and the fiber optics transmitter-receiver.

Final comment: At the back of the manual there’s an advertisement for a Win 2000 simulator of the EX-150. 9800 yen, Japanese only.

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