Ohms Law – Amps Volts Watts Relation

The most important Electrical Law is the Ohms Law, a proper understanding of which can help you make many designs. Troubleshooting Home Appliances or understanding Household Wiring is easy if you master this.

Volts is analogous to the pressure of a water in an Overhead Tank. The water head or height is like Voltage. The Pipe diameter and bends are like wire and its resistance, a water tap like a wirewound potentiometer. The rate of water flowing from the tap is like the flow of electric current in a wire.

Ohm’s Law – Watlow Electric The one i used to use, This would be in the back of the handbook.

The water drops are similar to units of charge, the quantity of water filled in a bucket is like the amount of charge stored in a small capacitor. The Underground Sump can be compared to a Big capacitor. The evaporation of water is like leakage of charge thru the dielectric in a cap. If you use the running water to power a home made paddle wheel turbine; This is like simulating an electric motor or heater in a water circuit, the rotary power got, can be analogous to the heater’s watts..

Ohms Law - Amps Volts Watts Relation

By Dmvstar (Own work) [CC-BY-SA-3.0], via Wikimedia Commons

Projects of Dick Streefland from De Bilt

usbtiny – Software USB implementation

USBtiny is a software implementation of the USB low-speed protocol for the Atmel ATtiny microcontrollers. Of course, it will also work on the ATmega series. The software is written for an AVR clocked at 12 MHz. At this frequency, each bit on the USB bus takes 8 clock cycles, and with a lot of trickery, it is possible to decode and encode the USB waveforms by software.


Other Atmel AVR Projects he built are

  • batwatch – Monitor for a solar panel car battery charger
  • webasto – Remote control of Webasto water heater
  • blink – Automatic turn signal light
  • nikon- Nikon Camera Remote Control

Projects of Dick Streefland from De Bilt

Dick Streefland, lives in Amersfoort, in the center of The Netherlands. He has some Atmel AVR Projects and he is a big fan of Linux. He started on a 6809-based home-brew system with the OS9 operating system from Microware.

Battery Level Indicator

This circuit uses a LM339, a quad comparator. LM339 can work on single or dual supplies, it has a open collector output that can drive 15mA, low power consumption. The circuit is an untested design but it should work. I did it as many searches were made in my webpages with these keywords.

Mains Voltage and Power Circuits – Similar circuits for Mains Voltage Monitoring.

There are many better circuits in the various circuit archives i have linked on the front page, you just have to look around. When you measure the open circuit voltage of a battery with a high impedance DMM (10M), the value may be a bit misleading. Apply a dummy load to bleed the battery a bit so that proper readings can be taken on Load. The load below is a 100 ohms wire-wound fusible ceramic resistor which will heat a bit when you test 12V batteries.
Battery Level Indicator

Theory of Operation.

R16 a 5W ceramic wire wound bleeder or dummy load. R15 is a part of an attenuator for obtaining ranges. D2 is a protection clamp diode. R10-D1 forms the 5V reference for comparators. Then an attenuator obtains 1.2, 1.4, 1.6, 1.8 V steps for each comparator. This circuit is similar to Audio Level meter or VU meter circuit.

Comparators in Interface Circuits

The comparator compares the battery sample voltage to the fixed reference step. If ‘+’ pin is more positive than ‘-‘, or is ‘+’ is more dominant, then output goes floating ‘open collector’, so No LED light . But if ‘-‘ is more dominant the output transistor of comparator goes low impedance or saturates or turns ‘ON’. But only spec current can be switched, do not compare with electrical switch ‘ON’. Also on a dual supply 0V is more dominant or positive compared with -12V, even though it appears -12V is a big number. The direction of current is what decides, all measurements are relative.

Webserver 8051 – Wickenhäuser Elektrotechnik

Build a true Webserver with only 2 chips. We did it! The used CPU (MSC1210Y4 from Texas Instruments) has 16kB Flash (up to 32kB available) and 1.2 kB RAM. Enough for a Webserver (provided you are using uC/51’s included TCP/IP stack).

Add Internet-Connectivity to your Applications with only a very few lines of C-Code. Many demos are included in uC/51, like: Webserver, E-Mail, Time-Client, TCP, UDP. Make Control System with remote Internet access to your sensors or actuatoors.

Embedded webserver FlexGate III

  • Easy-to-use stack, written with uC/51 V1.20
  • Everything “on board”
  • Best suited for uC/51 as development-hardware
  • uC/51-Tool-Chain Integration
  • CPU: 64kB Flash, 2 kB XRAM (32 kB as option), ISP, up to 5 MIPS
  • RS232 or USB (as option)
  • New V2.0 TCP/IP Stack included in uC/51 as 100% Sourcecode
  • Complete Low-Cost-Kits only 120.– EUR*:
  • FlexGate III module, RS232 cable, uC/51 Full Version, Power supply

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µC/51 V1.20.05 – Superoptimizing ANSI C compiler for the 8051 family