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.

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

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.

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.

delabs

Controlled Oven for stable Reference

This is a continuation of the previous two circuits. This circuit controls the temperature in a miniature oven that holds a stable dual voltage reference.

In colder seasons or locations this will maintain the temperature at a higher level. A mini fan in the equipment ensures external heat does not reach the oven, fan keeps the larger chassis cool.

Temperature Measurement and Control

This circuit may fail if the equipment is in very hot open locations, big heaters, hot machines or direct sunlight falls on equipment OR the Lab is not cooled to near normal ambient temperatures.

High Stability Reference Mirror

LM399 is a Precision Reference chip. From this a dual polarity mirrored reference is derived using OP07 op-amps. This assembly is mounted in a miniature oven to ensure temperature stability. 

The oven used Two Steel Boxes one mounted in another with Glass Wool In-between to reduce heater losses.  Steel was used to ensure excellent EMI-RFI Shielding. Both the outer and internal shell was earthed.

Instrumentation and Measurement Circuits

Regulated and Filtered Supply to this assembly further ensures consistent performance over the years and in various environments and seasons.

Differential amplifier for HV Power Supply

This is part of a precision High Voltage but Low current Power Supply for Testing leakage currents in passive devices. This Supply is a module for a  Automatic Test system in component inspection.

HV Precision Power Supply Circuits

Insulation of Transformers and the Isolation of plastic capacitors are best analyzed by applying a High Voltage and measuring the leakage currents.

These currents are in the order of nano-amps and pico-amps; values close to the bias-currents and leakage currents of devices. Some offsets and corrections can be done in software for the ATE systems.

SSR Solid State Relay DC Control

This is the newer version of NO - Normally Open DC Control SSR. It has a Constant current source that is more stable and robust.

You could use it to control AC powered Electricals like Heaters, Motors and Fans. It can also be used to Switch ON and OFF any Equipment, Control Panel or System.

You have to choose the correct current rating and heatsink needs of Triac. This is the older version below. It has a shunt current control. This new circuit above has a regulated current source.

DC-AC Solid State Relay or SSR - del30008

This is a basic output Module in control systems. It is faster than Electromagnetic relays but has some heating in the triac. Some designs with mosfets are also available. SSR with a IGBT - Insulated Gate Bipolar Transistors also can be made for large powers.

Generic LM317 Switching Supply

This was a common way LM317 was used to get a stable power for small devices. It is still useful for learning and some blocks of the circuit are still used today in modern industrial systems.

Before the SMPS took over as the default DC source in most systems; designers would use switchers to reduce thermal losses in Linear Supplies.

Linear Supplies have practically no noise or EMI_RFI (generation) issues . It is clean but not green. The efficiency is low. Transformer loss, heat loss in devices. The Product Safety is very high; but you need to use a Toroidal or Split-Bobbin Transformer for better isolation.

Power Electronic Circuits

The cost of these supplies are high as more copper is used, the space and weight is also considerable. Reliability and long term stability is excellent in these systems.

Dual Supply +5 and -5 using 555

In this circuit the 12 DC, two wire is converted to three wire +5 and 0 and -5 dual supply useful for op-amps or other interface circuits. You could use 7805 and 7905 low current TO92 package.

Regulated supply is essential for precision analog circuits.  This also could be used for signal conditioners that are built into the sensors. They are called voltage or current transmitters.

Negative supply also ensures total off or high-z in cmos analog switching. If you have crosstalk or leakage error in the Analog Mux; use a dual supply FET switches to turn total off and total on.

Instrumentation and Measurement Circuits

Datel (ge) mux chips had low on and off, but were expensive. Some cmos switches can improve with dual supply, but care to be taken that the negative voltage does not reach the ADC or uC stages.