1 INT Intermittent input
2 WIWA Wipe/wash (WIWA) input
3 LS Limit switch (wiper motor) input
4 PP Program pin
5 GND Ground
6 REL Relay output
7 VS Supply voltage
8 OSC RC oscillator input
Figure 2. Pinning
All times specified below refer to an oscillator frequency
of 200 Hz. Figures 2 to 9 show the dependencies of the
times upon battery voltage and temperature. The
temperature dependence of the oscillator frequency is
essentially determined by the temperature coefficient of
the oscillator capacitor. The temperature dependence of
the oscillator frequency can be reduced to minimum with
a slightly negative temperature coefficient (N100). The
capacitor used in figures 10 and 11 has a slightly positive
All times are permanently set and can be changed only
jointly within certain limits by adjusting the oscillator
frequency. See table 1.
The relay is energized for the time tON after the switch
INT is switched on with respect to VBatt and after
expiration of time tD (debounce).
The debounce time ranges between 60 ms and 80 ms. A
time period of 5 ms to 40 ms for internal sequence control
must be added (asynchronism between operating instant
and internal clock) e.g., the response time may range from
65 ms up to 120 ms.
If the limit switch of the windscreen wiper motor is
connected to Pin LS, the relay is energized as long as the
switch is at high potential, regardless of the relay on-time,
tON, i.e., the motor current in interval mode flows via the
relay contact only. In park position, the motor winding at
both ends is connected to ground via the limit switch and
the motor is decelerated immediately. The limit switch
input is debounced with tDL = 17 ms.
The relay on-time, tON, always elapsed – even if the
interval switch was opened beforehand.
The interval pause tINT = 10 s follows tON. Opening of
switch INT causes a debounce time, tD, and reclosing
results in the relay on-time, tON, after tD.
Wipe/Wash Function without Pre-Wash
Delay (PP connected to GND)
The water pump is switched on when the switch WIWA
is pressed and, after the debounce time, tD, the relay is
energized. After-wiping time tAW = 5.8 s starts as soon as
switch WIWA is opened and the debounce time, tD, has
expired. If the limit switch is connected, the relay remains
energized until the wiper arm returns to park position, i.e.,
the motor current flows via the relay contact only.
Wipe/Wash Function with Pre-Wash Delay
(PP connected to VS)
In wipe/wash mode, the relay is energized after a delay
time. The water pump can spray water onto the wind-
screen during the delay time, tDEL.
The on-delay time of the U2641B is:
tDEL = tD + 0.84 s = 0.91 s
If switch WIWA is closed longer than tD but shorter than
tDEL, the after-wiping time, tAW, starts after expiration of
tDEL. The wipe/wash function with or without on-delay
tDEL can be selected by programming PP.
PP connected to GND:
PP connected to VS:
without pre-wash delay
with pre-wash delay
The after-wiping time, tAW, is re-triggerable in both cases.
Intermittent and Wipe/Wash Mode
The wipe/wash function has priority over the interval
function. If switch WIWA is closed during the interval
Rev. A2, 02-Dec-97