Micro
Subway
PWM Generator - PWM1
This PWM stand-alone chip is of low cost, low component count, and very easy to use. It generates a Pulse Width Modulated waveform by easily manipulating the ON-OFF timing via four separate momentary switches. Here are the functions of the four different switches used:
1. Switch 1 increases the ON time when pressed and released.
2. Switch 2 decreases the ON time when pressed and released.
3. Switch 3 increases the OFF time when pressed and released.
4. Switch 4 decreases the OFF time when pressed and released.
|ֿֿֿֿֿֿ|ַַַַַַ| <
ON-OFF (or HI-LOW)
It
also can be setup to cause a (10, 100, 1000, 10,000) times jump in increasing
or decreasing the ON-OFF timing (via the jump switch). The jump is accomplished
4 times. Each time the jump SW is depressed the multiplication is shifted up as
per (10, 100, 1000, 10,000) times. When it reaches 500 times it rolls back to
10 and so on. This feature enables it to serve a multiple of applications that
are only limited by your imagination.
At
power up the multiplication factor is 1 (1 ms). When jump switch is depressed
the delay factor (ON or OFF) jumps to a factor of that which corresponds to the
press number of the jump switch. An easy way to verify the frequency is to
connect the output to the oscilloscope or a piezo/speaker element. When the
frequency is low you almost hear clicks, when the frequency is higher you hear
constant tone. A maximum ON + OFF time of 1 minute (60,000 ms) can be
accomplished.
Examples:
|
Multiplication Factor |
ON
or OFF Press
1 |
ON
or OFF Press
2 |
ON
or OFF Press
3 |
ON
or OFF Press
(MAX) |
|
|
|
1 |
1
ms |
2
ms |
3
ms |
10 |
|
@
power ON |
|
10 |
10
ms |
20
ms |
30
ms |
100
ms |
|
1st
jump press |
|
100 |
100
ms |
200
ms |
300
ms |
1000
ms |
|
2nd
jump press |
|
1000 |
1000
ms |
2000
ms |
3000
ms |
10,000
ms |
|
3rd
jump press |
|
10,000 |
10,000
ms |
20,000
ms |
30,000
ms |
60,000
ms |
|
4th
jump press |
|
|
|
|
|
|
|
|
If
you need different multiplication values than (10, 100, 1000, 10,000) or any
other feature then please email us and we will design the
chip that best fits your need.
Figure
1. Basic
operation of the PWM1 chip.
Examples
are controlling the speed of the motor, brightness of a light, periodic
activation of devices, a serine, a timer, and so on.
Note:
you can add an external op amp to the output of the PWM1 or use a transistor
driver if you are driving high power load. Also you may connect a piezo element
directly to the output if you only need to produce an audible sound with
variable frequency and effects. You may use 4.7 K for all pull up resistors and
22 pf ceramic disk caps for C1 and C2. All switches shown are Normally Open (SW
- N.O.)
Caution: Do not connect the output
directly to the ground or the power supply, this may damage the chip.
|
Pin
# |
Function |
|
|
A |
Increase
ON time |
ַַ|ֿֿֿֿֿֿ|ַַ |
|
B |
Decrease
ON time |
ַַ|ֿֿֿ|ַַַַַַַ
|
|
C |
Increase
OFF time |
ֿֿ|ַַַַַַ|ֿֿ |
|
D |
Decrease
OFF time |
ֿֿ|ַַַ|ֿֿֿֿֿֿ |
|
E |
Jump
function |
Multiplies
ON-OFF |
|
V |
+5
VDC or + 3 VDC |
Special
order |
|
G |
Ground |
GND |
|
O |
Output
of the PWM |
|
|
X1 |
Crystal
pin 1 |
4
MHz xtal |
|
X2 |
Crystal
pin 2 |
4
MHz xtal |
Electrical
Specs:
|
Max
VDC |
7.5
VDC |
Not
to exceed 7.5 Vdc |
|
Op
Temp |
-25
to 125 °C |
Ambient
– when biased |
|
Current
Supply |
2
to 4 mA |
From
bat. |
|
Output
current |
0
to 25 mA |
Depends
on PWM |
|
Output
Voltage |
2.3
or 4.3 VDC |
MIN
– Special order |
|
Operating
Voltage |
3
or 5 VDC |
Special
order |
Note:
Values depicted above may slightly deviate when operating under certain conditions
(very low load impedance or high temp.)
Unit
price:
1
to 10: $4.99
11
to 1000: $3.99
1000+:
$2.99
Micro Subway
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