44
2.7 Binary memory
Circuit 19:
An electronic brain cell
Setup information
Install the two transistors as shown in
Fig. 2.19.
Then install the green LED. Now it is time for the six resis-
tors. Finally insert the five jumpers and the two jumpers which will function as switches (shown in dashed
lines to identify them easily). For your guidance we have labelled the “switches” with “On” and “Off”
accordingly. Check the placement on the board again and only then connect the battery.
Components required:
2 x 2N3904 transistors,
1 x green LED, 3 x 1 k
Ω
resistors, 1 x 2.2 k
Ω
resis-
tor, 2 x 100 k
Ω
resistors,
1 x breadboard, 1 x 9V bat-
tery with clip connector
Fig. 2.19:
An electronic brain cell
Experiment
If everything is wired correctly, both “switches” are open, which means that one end of our two jumper
wires is not connected. “Close” or insert the jumper wire marked
On
for a moment. The green LED light is
steady on. When you “open” the
On
switch again, the diode will continue to glow.
The circuit (called bistable or two-state flip-flop) will remember that at some point the
On
“switch” was
activated. You can reset the circuit, by momentarily “close” the
Off
switch. This will turn the green LED off
again. This is a fundamental building block used in modern digital electronics. A bistable flip-flop stores a
piece of information for an unlimited time. It knows two stable states, namely
On
and
Off
(digital technol-
ogy calls these states
high
and
low
or
1
and
0
). Each of these states can be triggered by an external control
signal. Quartz watches, mobile phones and in particular Tablets and PCs have these basic circuits in large
numbers.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.19.
Содержание ELECTRONICS EXPERIMENTS BOX
Страница 4: ......
Страница 251: ...253 Fig 3 27 Circuit 27 4 seconds switch off delay Fig 3 28 Circuit 28 20 seconds switch off delay...
Страница 258: ...260 Fig 3 42 Circuit 42 Active 8 5V battery monitor Fig 3 43 Circuit 43 Active 7 8V battery monitor...
Страница 260: ...262 Fig 3 46 Circuit 46 Meters for 1 5 V Zener diodes and higher Fig 3 47 Circuit 47 Discreet 2 2V Zener diode...
Страница 261: ...263 Fig 3 48 Circuit 48 Discreet 2 9V Zener diode Fig 3 49 Circuit 49 Discreet 3 7V Zener diode...
Страница 265: ...267 Fig 3 56 Cir cuit 56 Audio limiter Fig 3 57 Circuit 57 Amplifier for a storm detector...
Страница 269: ...271 Fig 3 64 Circuit 64 Stabilizer for 1 9 V Fig 3 65 Circuit 65 Stabilizer for 2 5 V...
Страница 275: ...277 Fig 3 80 Circuit 80 Quiztimer 30 seconds Fig 3 81 Circuit 81 Handy diode tester...
Страница 290: ...292 Fig 3 118 Circuit 118 HF watch dog with LED indicator Fig 3 119 Circuit 119 HF watchdog with moving coil instrument...
Страница 295: ...297 Fig 3 130 Circuit 130 4 seconds switch on delay Fig 3 131 Circuit 131 15 seconds switch off delay...
Страница 298: ...300 Fig 3 136 Circuit 136 NAND gate with moving coil instrument Fig 3 137 Circuit 137 Input level Mixing console...
Страница 300: ...302 Fig 3 140 Circuit 140 Electrometer with moving coil instrument Fig 3 141 Circuit 141 Simple AM Radio...
Страница 315: ...317 Fig 3 179 Circuit 179 HF generator 150 kHz Fig 3 180 Circuit 180 HF generator 420 kHz...
Страница 324: ...326 Fig 3 202 Circuit 202 3 seconds switch on delay Fig 3 203 Circuit 203 7 seconds switch on delay...
Страница 325: ...327 Fig 3 204 Circuit 204 Piercing siren sound with Piezo element Fig 3 205 Circuit 205 Discrete Operational ampli fier...
Страница 328: ...330 Fig 3 210 Circuit 210 Discreet 5 2V Zener diode Fig 3 211 Circuit 211 Discreet 7 4V Zener diode...
