Professional speedometer circuits are complicated and expensive, and general enthusiasts are restricted by economic conditions and cannot afford to buy. The author designed a simple electric tachometer that can be used for speed testing of general objects.
The speedometer circuit shown in Figure 1, the circuit is very simple, using only a triode single-tube amplifier circuit, when the speed motor M is driven, it will produce a weak current, the current through the transistor Q amplification, promote micro-A The meter A indicates that the faster the measured object rotates, the greater the current generated by the speed-measuring motor, and the larger the meter's reading, which is used to adjust the size of the meter indication.
During production, select the components as shown in Figure 1. M is a miniature toy DC motor; A uses a 100uA meter, preferably in the middle of the dial, so that when the speed is measured, it is not subject to the direction of rotation of the measured object. Limit, otherwise, the test direction will be wrong, the hands will be reversed, damage the meter; W can be used with a linear potentiometer power switch, so that it is easy to draw a uniform test gear scale marks on the panel; power supply can choose 9V laminate battery . The simple circuit does not need to make the printed circuit board, and it can adopt lap welding. After soldering, the whole device is in an appropriate small box. The appearance is shown in Figure 2. The speed measuring head adopts a flexible rubber connector, such as the tape press wheel of the recorder, and is tightly sleeved on the motor shaft.
After the production is completed, calibrate with a standard tachometer and mark the scale of each test range on the panel. Refer to Figure 3.
When using, press the speed measuring head on the measured object, and adjust the W button so that the pointer is at the 2/3 mark of the range of the head, and with the test mark value marked with the W button, the speed of the measured object can be estimated. For example, if you want to test the speed of the motor, just press the speed head on the axis of the motor shaft.
This tachometer can also be used to test wind speed, liquid flow rate, and other items in conjunction with appropriate speed measuring heads. Fans can use their imagination and design their own. No more fees are spent here.
- Universal fit: compatible with all automobiles, boats and devices equipped with a 12V power source
- CIRCUIT PROTECTION: Power relay-safety protection and conversion circuit. Blade fuse protects the circuit when overcurrent or short circuit occurs.
- ILLUMINATED SWITCH: 3 pin on/off rocker switch with red indicator light when truing on, easy to turn on or off, has been passed test of 5, 000 times pressing.
- TWO AVAILABLE LEADS: With 2 sets of light output connectors for dual lighting fixtures less than 180W, the connection is more stable.
- PACKAGE INCLUDE:1 x Wiring Harness Kit ,1 x Instructions,
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Dongguan YAC Electric Co,. LTD. , https://www.yacentercns.com