Solid-State Windshield-Wiper Delay

Posted on Aug 22, 2012

In the wiper-delay schematic shown, with the ignition on, Dl maintains regulated +12 Vdc. When SI closes

Click here to download the full size of the above Circuit.

, CI bypasses transients and passes this +12 Vdc to divider R2-R3, producing a TTL high at pin 3 of IC1, a 4013 CMOS dual leading-edge triggered D-type flip-flop. Filter R4/C3 keeps IC1 from triggering erroneously when the ignition is on. When SI is pressed, output Ql (pin 1) of IC1 latches high, turning on Ql, which conducts via R5, turning on IC2; LED1 indicates power, and R6 sets the current. Because IC2 depends on Ql for power, IC2 stays off until Ql turns on. The left half of IC2 is an astable, with its delay set by R7, R8, Rll, and C4. The right half of IC2 is a monostable, with its pulse duration set by R9 and C5. With the values used, you might expect Rll to vary the delay from about 15 to 84 seconds, with a 2.42-second monostable pulse operating the wiper blades on each cycle. However, the actual delay will range between 2 to 18 s, with a 1-s monostable pulse on each cycle. That discrepancy stems from the fact that IC2 is being fed from the emitter of Ql, rather than directly from the regulated +12-V supply. Transistor Ql acts as an active current source, charges and discharges C4 faster than it ordinarily would. The astable output (OUTi, pin 5) is tied to TRIG2 (pin 8). When OUT2 (pin 9) becomes high, Q2 is biased via RIO and current flows through RY1, with D2 dissipating back-emf when RY1 shuts off.

Leave Comment

characters left:

New Circuits

Zero consumption Anti-theft High power Code Switch for E-Bike Batteries

This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
Ultrasonic distance finder circuit

The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Simple Metal detector circuit with CD4030

Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Fully automatic watering circuit for flower pots

Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
Simple deep searching metal detector circuit

The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
Sub-Harmonic Bass Converter for Electric Guitars

The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
Echo Depth Sounding Sonar for Boats

In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
100W HiFi Audio Amplifier Circuit

This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
Plant-Pot Water Level Indicator Circuit

A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....

Create NOW your QR MENU for your Restaurant / Hotel / Bar / Caffe,

Comprehensive ordering/paying features. fully personalized to suit your Business.

Update Anytime! Easy and Simple!

Popular Circuits

Sound Effects Generator

This circuit uses a UM3561 IC to produce four different sound effects. Nothing too complicated...

Frequency Peak Detecting Probe

This is a handy companion for a digital voltmeter. Its allowed me to do a lot of things I used to...

RF power and VSWR meter

The Inter-Power SWR-5 - upper right - "isn't worth a penny". Got it from a mate to use with a...

Voltage-Programmable Current Source

This, circuit is a programmable current source in which op amp LT1102 (Linear Technology Corp.)...

simple stabilizer circuit diagram

A aerial affection ability accumulation with a continuously capricious stabilised achievement...

The 145 Theremin

Since the publication of the type 144 theremin project article in September, 1998, many of them...

Simple Infrared Control Extender

In some cases, it is desirable to extend the range of the available control and this circuit fits...

Three-phase motor overcurrent protection circuit

A three-phase electric motor is over- current protection circuit. How it works: This example...