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Two different values potentiometers are provided to allow for better tuning
of your timer. The 50k pot allows for fine tuning when more precise pulse
widths are required. The 500k pot allows for greater time ranges.
The Monostable Pulse Width chart shows the Pulse Widths available with
provided components. The R4 Minimum column shows the minimum (0
ohms) Pulse Width for both provided potentiometers (50K and 500K) and
the capacitor resistor combination shown in the left most column. The R4
= 50k/R4 Maximum column shows the maximum Pulse Width of the 50k
pot and the resistor capacitor combination shown in the left most column.
The R4 = 500k/R4 Maximum column does the same for R4= 500k.
The Astable Timing Chart works the same way as the Monostable Pulse
Width chart in addition to Pulse Width it also provides Rest Time, Total
Time, and Frequency. This chart it assumes that R4 = R6 and R5 = R7
which is not required. You may mix and match the potentiometers and
resistors as you wish.
37. Install R4, either the 50k (marked 503) or 500k (marked 504) potenti-
ometer. Make sure this part is square and flush to the board.
38. Install R6, the other timing potentiometer either the 50k (marked 503)
or 500k (marked 504).
39. Install R5, using the calculations or charts select your part value.
Used the parts list description of color bands (Example 1K marked brown-
black-red) to select the proper resistor.
40. Install R7, for this part follow the instructions for R5 above.
41. Install C2, using the calculations or charts select your part value. If
you select the 0.1uF capacitor (marked 104) polarity is no concern. If you
select the 10uF (marked 10uF) or the 1000uF (marked 1000uF) electro-
lytic capacitor observe correct polarity.
UT5A 18
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