It`s based on an LM2917 and an SCR, which has the very nice side effect of being impossible to generate any mis-timed sparks, a highly desirable attribute for high output rotary engines. When the limit is reached by accelerating to the rev limit, the transition is smooth and causes no backfiring. (BUT it has the potential to damage the exhaust fro
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m a backfire if the engine is downshifted and consequently over-revs; due to unburned air/fuel mixture coming from the engine that may be ignited by combustion when the RPMs fall below the limit). The heart of the circuit is a National Semiconductor LM2917 Tachometer IC which detects the engine RPM and when it exceeds a given level the `load` SCRs are turned on which reduces/eliminates the spark energy and hence the engine power. The input signal comes via the 10k, 22k resistors and C1 (. 02u). This forms a signal shaping network that protects the IC input and filters out any high frequency signals (eg coil ringing). This filtered input is compared against a 0. 6volt reference formed by D1 and it`s 10k resistor. This further serves to minimise false triggering. Now there is a signal which pretty much represents a cleaned up version of what`s happening at the points. This passes into a "Charge pump" with C2, C3 and the 100k resistor. This converts the frequency of the input signal (i. e. the engine RPM) into a voltage level. From the charge pump, this voltage level is compared with the preset voltage level (the 50k "Set rev limit" potentiometer - the 15k preset associated with this is optional, and sets the absolute maximum rev limit. This is handy if the rev limit is changed depending on the situation). When the tachometer voltage exceeds the limit voltage (i. e. the ENGINE RPM IS OVER THE LIMIT), the transistor in the...
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....
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....
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....
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....
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....
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,....
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....
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....
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.....
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