• Tech Ads

Beagle Board – Create Open Embedded Devices

The Beagle Board is a low-cost, fan-less single-board computer based on Texas Instruments OMAP35x processors featuring the ARM Cortex-A8 core.

Beagle Board – Create Open Embedded Devices

The USB-powered Beagle Board is a low-cost, fan-less single board computer that unleashes laptop-like performance and expandability without the bulk, expense, or noise of typical desktop machines.

BeagleBone Black – Boot Linux in under 10 seconds and get started on development in less than 5 minutes with just a single USB cable.

BeagleBone Black

OMAP3530 processor highlights:

Over 1,200 Dhrystone MIPS using the superscalar ARM Cortex-A8 with highly accurate branch prediction and 256KB L2 cache running at up to 600MHz. HD video capable TMS320C64x+ DSP for versatile signal processing at up to 430MHz.

Buy a BeagleBoard at Digikey

Some Projects on BB

beaglelab – BeagleLAB is an Embedded Developer’s Workbench

BeagleBot – Beagle powered robot – A small experimental robot with Beagle Board as it’s heart.

Mixed Circuits Analog with Digital

Mixed Circuits Analog with Digital

Here are some circuits that have both Analog and Digital Signals in them. At one time i wanted to make reed relays, it was a good spot to be in, as it was used in Telecommunications. Even Small Office EPABX systems would have quite a Few of them. It was Simple, get some reeds from OKI and wrap them up in some copper coil and Pot them in a plastic can with epoxy. Before i could get even some trials out, the market was flooded with Good Quality Reed Relays from many.

So the Lesson, “Time to Market” should be minimum without sacrificing Quality. That brings us to another metric, The TTM/Q Ratio ;-) . This should not be mixed up with “Time to Exhibition or Trade Show”.

Fluid or Water Level with Reed Relays

“Reed Relay. It was invented by Dr. W. B. Ellwood at Bell Labs in 1936. Contacts are in a sealed glass tube filled with inert gas like in a bulb, so they do not corrode. It is faster than regular relays and as no spring is used it has a longer mechanical life. The two contacts are ferromagnetic blades plated with rhodium. When you take a magnet close by, the contacts touch each other. You can also put the reed in a coil, then when you energize the coil the reed operates. Used in telecommunication.OKI is one manufacturer of this type of component. “

Some Circuits on above pages are..

  • Voltage to pulse converter using opamps
  • Analog Section of 8751 based flowmeter
  • Voltage to pulse converter impulse counter
  • 16 channel analog multiplexer
  • 8 channel analog mux with sample hold
  • Digital Control for 8 channel analog mux

Instrumentation and Measurement Circuits

Instrumentation and Measurement Circuits

T&M and Process Control Instrumentation have many things in common; but the conditions in which a Industrial Instrument works, may be very unfriendly.

Industrial Instruments are used both in Clean-Cool Control Rooms and also in a corrosive, humid, hot and vibrating industrial environment. Even high levels of Static, Magnetic influences in conjunction with spikes and brown outs can be expected.

Test and Measurement instruments are of two types, by way of its usage; Portable and Benchtop. Portable Instruments will consume low power, insulated and rugged. The Product Safety features are more stringent as they are HandHeld or slung over the shoulder. Some features and specs are sacrificed. The Benchtop version has more front panel space and can interface with other instruments or systems. More accuracy and features can be accommodated in this.

Basic Measurement

Other Circuits on this page are – in PDF

Simple MilliVolt Source, 0-2V to 4-20mA Converter, Analog averaging circuit with Opamps.

Electric double layer capacitor an eFlywheel

The Electric double layer capacitor has the main use of a Charge Reservoir. That means a large amount of electrical charge in a small footprint.

These charge/discharge quickly unlike the battery, There is no Electrical Energy to Chemical Energy Transformation and back, like in batteries. It may need caution in design and usage as they may carry a lot of punch.

Also known as Ultracap, Goldcap, Supercap – Electric double layer capacitor, In Farads, like batteries, Energy Reservoirs or eFlywheel.

In Product Safety terms; The Battery has a Internal Resistance, but a Supercap does not. When used in Values like 100F and is fully charged, an Internal or External Breakdown of Insulation or Short Circuit may Occur. The Heat Generated is Enormous. Murphy’s Law says such things happen..

Supercap at Wikipedia

Electric Double Layer Capacitor (EDLC) or SuperCapacitor

DLCAP – Electric Double Layer Capacitor – Nippon

They have a range of Supercapacitors upto 2500F at 2.5V and Modules like 400F and 15V. There are two types Prismatic and Cylindrical. In comparison to batteries – multi-million cycles of charge-discharge is possible.

EverCAP – Double Layer Capacitors – Nichicon

They have two types, High Power Density for a large current discharge. High Energy Density for a long backup time. Over a million Charge/Discharge cycles. High Efficiency. Capable of fully discharging to zero volts.

Some things to note for a design engineer. The EDLC or Electric Double Layer Capacitors …

  • Specified Endurance and end of life.
  • Excess Vibration can alter Specs.
  • Caution – The maximum temperature.
  • Specs are dependent on Temperature.
  • Maintain Low ripple current on Charge/Discharge.
  • It is Polarized like a Electrolytic cap.
  • Not Hot parts or Heatsink near cap.

The Double Layer Capacitors developed by WIMA are storage capacitors with highest capacitance values in the Farad range.

GTO Capacitors – WIMA

They are among others suited to serve as batteries, can deliver considerably higher currents for a short time, however, and are maintenance free.

SuperCapacitors – WIMA

These EDLC supercap has one-tenth of energy, but delivers over 10 times of power due to ultra low ESR. In Comparison with a Battery. A Lifetime of over 500,000 cycles.

Xelled Supercapacitor – Vinatech

Some Specs

  • Rating 2.5V / 2.7V
  • High power density (low internal resistance)
  • High electrical current, instant power back-up applied

Read more about Supercapacitors.

Battery Charger and Rechargeable Batteries

The main Types of Rechargeable Batteries are NiCd – Lead Acid – NiMH – Lithium ion. The Gel Lead Acid Battery is Termed Maintenance Free and may have to be treated differently for charging.

List of battery sizes – Wikipedia

Battery Types and their Sizes

4.5 Volt – D – C – AA – AAA – 9 Volt – SR41/AG3 – SR44/AG13

Battery Charger Circuits and Resources

Solar charger for lead-acid batteries
The charger will stop charging once a pre-set voltage (temperature compensated) has been reached, and recommence charging when the voltage has dropped off sufficiently.

12 Volt Gel Cell Charger
When a discharged gel cell is connected, the charger goes into a fast charge mode at a fixed rate of 400 ma. After the chip detects the voltage leveling off or when 4 1/2 hours has elapsed.

Temperature Controlled NiCd Charger
This circuit is for a temperature controlled constant current battery charger. It works with NICD, NIMH, and other rechargeable cells.

Battery charger 150-1700 mAh with PIC16F876
This is the extension of the simple battery charger to different battery capacities. The software and the controller are largely identical.

MAX846A Cost-Saving, Multichemistry, Battery Charge Chip
In its simplest application, the MAX846A is a stand-alone, current-limited float voltage source that charges Li-Ion cells. It can also be paired up with a low-cost microcontroller (┬ÁC) to build a universal charger capable of charging Li-Ion, NiMH, and NiCd cells.

Rechargeable Batteries and Chargers
There are three types of rechargeable batteries. They are Nickel-Cadmium (NiCd), which are the oldest type; Nickel-Metal Hydride (NiMH), which were developed around the same time that low-cost digital cameras were invented.

Interface ICL7135 Voltmeter to Atmel 89C52 or PC

This circuit is an interface between 89C52 of Atmel with 7135 of Intersil. With This circuit you can read analog data of both polarities you can change the range scale with extra circuits, you can store data on a EEPROM or send them to PC thru RS232 or Comm port.

ICL7135 to Printer port Interface

The four Digit Drive outputs and four BCD outputs of the Multiplexed Display Driver of 7135, along with A-D status output which is also four, are routed to four input pins on printer port via three 74HCT373 Digital Switches. This is because we have less Input pins on Port and 4 are shared by making one 74HCT373 transparent and others High Impedance when PC takes a reading. So the three sets of four outputs of 7135 can be read sequentially.

74HCT139 U9A which is controlled by the PC program can select U3, U4 or U5 for sending data to 4 pins on printer port. Data sent on the eight output pins of printer port can be latched by U10B into U6. This eight outputs of U6 can drive relays or lamps.

See also – Milli Volt Source for Printer Port.

Serial Interface a 80C31 to ICL7135

uC Input and Output I/O is Keyboard and LCD when you build a Calculator or a Text/Morse Communicator. When you control a motor it is Drive/Speed and Direction for Motor and Tacho or Opto Counters for Feedback. In both cases you have Input and Output which is Logic or Analog which has to reach the CPU.

Getting the analog into the uC is done here with ICL7135, with a simple two wire serial interface. Here a Pair of CD4538 MMV is used to shape the pulse just right for uC data transfer,…

AT89C52 Parallel Interface to ICL7135

This circuit is an interface between 89C52 of Atmel with 7135 of Intersil. With This circuit you can read analog data of both polarities you can change the range scale with extra circuits, you can store data on a EEPROM or send them to PC thru RS232 or Comm port.