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Tuesday, April 30, 2019

Fluid or Water Level Indicator

The Reed Relay based Float Switches are used in Automobiles and even corrosive and volatile fluids. This can also be used to indicate level of water or operate pumps.

The reeds are hermetically sealed in glass, Like the Incandescent bulb. The signal switched by reed also should be a few mA or even uA. This makes is safe in Volatile fluids, where sparking can cause fires.

Fluid or Water Level Indicator

This is a way by which you can monitor the level of fluids like water in a tank. Based on data from the sensor you can control things like solenoids or motors as required or even turn on a buzzer, hooter or annunciator in a control panel.

Water Level Indicator with Reed Relays

Then you need to assemble a small circuit within the long plastic pipe. Many reed relays with a chain of resistors in series has to be inserted in the pipe. The resistor and the glass reed relays should be in different levels of the pipe where you need an alarm or indication. Seal the pipe hermetically at both ends with epoxy resin after taking out a shielded cable of just 2 wires + 1 ground shield.

Monday, April 15, 2019

Analog to Digital with a V-F LM331

A Low cost A/D with a Potential of 5KV Isolation from Computing elements by use of Normal/Special Opto-Couplers. This can give better resolution and accuracy than a 8 bit A/D. may be close to 10 bit A/D. Added advantage is that you can optically isolate the inputs.

Analog to Digital with a V-F LM331

Suppose your temperature sensor touches a heating element OR your speed sensor is subjected to a shock from a defective motor with earth line broken. Such situations happen in the field, even at home or lab. Sometimes it is carelessness, other times it is wear-tear. Many times it is breakdowns, accidents etc. So do not let the High voltage to get at your Microcontroller Board.

More about Embedded Micro here - Hyper Embedded

Monday, April 01, 2019

Regulated Power Supply 24V with 2A

Here is a simple to build regulated power supply. The two diodes are to boost the 24V to 25V DC. It uses regulator 7824 and TIP2955 PNP Transistor to boost current.

24V and 25V Power Supply with 2A Current

1. choose a transformer with a close match of what is available.

2."100V 3A" at the bridge is the minimum diode rating also(or use 4 x 1N5408). "100V 3A" is also minimum bridge rating use a close match.

3.to make a bridge with 4 diodes refer my other circuits, there are many.

4. 22V AC leads to around 30V unrectified DC which is good, if the 30V becomes more, the heatsink needs to be very big.

5. the ground of regulator is lifted by (0.7*2) by 2 diodes to provide 1 V above 24V, as 25V regulator does not exist. the power supply 'neg' can be grounded or earthed,

6. the supply is a+25 V from ground or negative, but things are only relative.

7.if you need a dual supply 3 terminal , that is ground +25 and -25 then for -25 one more circuit using 7924 and tip3055(npn) has to be made.

8. use any high current pnp transistor (5A) you have put a heatsink with heatsink compound.

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