1381*

From BEAM Robotics Wiki

[edit] 1381*

1381s are CMOS voltage-controlled triggers -- these "gate" a source until the voltage is above some "trip" limit, at which point it is allowed onto a third pin. These chips are discriminated by the voltage at which the 1381 triggers, with a single-digit suffix (a.k.a., its "rank") on the part number corresponding to the trip voltage:

Rank (suffix)	Trip voltage (V)
C	2.0
D	2.1
E	2.2
F	2.3
G	2.4
H	2.5
J	2.7
K	2.8
L	3.0
M	3.2
N	3.4
P	3.6
Q	3.8
R	4.0
S	4.2
T	4.4
U	4.6

The triggers operate in the range between the listed value and +0.2V (+0.3 from J up) above it (i.e.: a 1381C will trigger between 2.0 and 2.2V).

Generally, 1381*s are used to build very efficient solar engines, their job being to determine when the solar engine should "fire." The tradeoff in trigger value selection comes in that higher voltages lead to more-energetic activation, but at a less-frequent rate. The 1381J is the most commonly used, although of course, you can pick something different according to your needs. You can also use a diode in series with a 1381 to raise its trip voltage by 0.7 V.

1381*s generally come in the T0-92 package (see diagram above for pinout).

See the data sheet for more details on this chip. The datasheet as well as the 1381 are usually available from long time BEAM supporters Solarbotics

Note: Can interchange this part with TC54

NOTE: These are getting harder to find, you might have better luck finding its European cousin, the TC54 – for details on it, see its data sheet.