This is a mains 230V AC load current indicator and is a LIVE CIRCUIT, so take care. The Resistors have to be a fusible ceramic wire wound.
More at Mains Voltage and Power Circuits
This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try. You should use the fuse of 1A a slow blow if you want but it is very important. You can design the shunt R3 and Fuse rating as required by your load.
U1 7555 is a CMOS version of 555. The 555 here is in Astable Oscillator mode, C1 and C4 are decoupling capacitors 0.1uF value, ceramic disc.
Mixed and Interface Circuits
The output is around 100kHz, If C3 is plastic or mica the frequency output will be stable with temperature. It is better to use a crystal oscillator.
This is a LED Analog Meter, This can be used as a Resistance Meter and Low Impedance Voltmeter for Battery Levels.
Resistance measurement Current Source
To measure battery voltage, the R5-R12-R17 etc. part of the Reference Resistor Divider Network can be modified to suit. Shown here is for 4 LEDs, Use Three LM324 for 12 or More LEDs and Cascade as shown.
In the circuit, use only metal film resistors (MFR) of 1 per cent tolerance, as this is an instrumentation application. Power supply should be a stable +5V, -5V supply, for which one can use 7805 and 7905 regulators.
Thermocouple Temperature using DPM or DMM
The inputs TC+ and TC- terminals should go to a 4-way barrier terminal block, the 2 extra terminals are used to mount TH1 Cu thermistor. This forms an isothermal block, which is good enough.
This is a Test Circuit for Logic Analyzer software, with the Simple port circuit. The VB Logic Analyzer works, but is just an example program to test and learn.
Test Circuit for Logic Analyzer software - del20006
The speed at which the logic state changes say like 10 M Hz while probing even a PIC or 89C51, is too fast for this circuit. For that, the incoming data has to be spooled or stored in RAM at real time, by the external Hardware itself.