3-1/2 Digit ICL7107 DPM Digital Panel Meter

This is a Digital Panel Meter based on ICL7107. This was the workhorse Digital Readout chip before Low power uC designs were developed. Even now it is the easiest way an analog parameter can be displayed in an instrument.

Instrumentation and Measurement Circuits

3-1/2 Display is just enough resolution for recording process data or troubleshooting equipment. With 4-1/2 you notice the problems of thermoelectric EMF of probes and connectors. That is one reason gold plating is used another being low contact resistance. In 4 1/2 the reading can change due to contact resistance too, if the input impedance of the analog signal conditioning is low or the protection diodes, RC filter caps are leaky.

ICL7107 DPM Digital Panel Meter

When you measure an analog parameter from a sensor; you attenuate or amplify it, to scale to the A/D converter range. You also need to protect or isolate the analog front end from high energy mis-connections, which will happen during field use. The operator should not get injured from any high energy leakage while measuring.

Resolution is the finest detail you can enumerate in a parameter or object. You can say the crowd was 3000 or 4000 people. Here 1000 is the resolution, finer data does not matter here. You would also hear things like, there were 80 to 90 boys in that classroom. 10 is the resolution there.

Accuracy is how precise a statement or number is. If there was 85 boys in that class, the above statement is accurate. If there was 65 boys, the measuring method or process needs calibration or examination.

In this circuit, the plastic caps should be of very low leakage. Multilayer plastic caps are good for instrumentation.

The MOSFET in Power Electronics

delabs Notes – In a Circuit Module, if all Power and Signal Polarities are reversed. All NPN to PNP, All N-Channel to P-Channel and Vice Versa. All Diodes and Caps too turned around. This Topsy Turvy or Mirror Design ought to work in Theory. It has worked for some circuits in practice too in my experience. ?

Some believe that N-Channel is more Robust than the P Type. In Bipolar Transistor NPN is more trusted for the final output stages. The NPN Transistor and N-Channel turn-on by a Positive control bias. It may be inappropriate to say this mosfet is NPN or PNP.

The MOSFET in Power Electronics

The traditional metal–oxide–semiconductor (MOS) structure is obtained by growing a layer of silicon dioxide (SiO2) on top of a silicon substrate and depositing a layer of metal or polycrystalline silicon (the latter is commonly used). As the silicon dioxide is a dielectric material, its structure is equivalent to a planar capacitor, with one of the electrodes replaced by a semiconductor.

If the MOSFET is an n-channel or nMOS FET, then the source and drain are “n+” regions and the body is a “p” region. If the MOSFET is a p-channel or pMOS FET, then the source and drain are “p+” regions and the body is a “n” region. The source is so named because it is the source of the charge carriers (electrons for n-channel, holes for p-channel) that flow through the channel; similarly, the drain is where the charge carriers leave the channel. MOSFET – Wikipedia

This application note discusses the breakdown voltage, on-resistance, transconductance, threshold voltage, diode forward voltage, power dissipation, dynamic characteristics, gate charge and dV/dt capability of the power MOSFET.
Application Note AN-1084 Power MOSFET Basics – IRF

A MOSFET is a transistor. It is a Metal Oxide Field Effect Transistor. Here are the symbols for FETs and MOSFETs: The MOSFET How the MOSFET works

The conductivity of the path from Source to drain is controlled by applying a voltage between the gate and the body of the semiconductor. N-channel enhancement MOSFET

See this simple circuit that explains everything
n-channel MOSFET switch – George Watson, Univ. of Delaware, 1996.

Clean Rooms and Electronics

Clean rooms and Dust free environment is a must for Precision Mechanical Engineering. It is not MEMS or nano sizes, even micron sizes accuracy in parts can be affected by Dust and Humidity.

In Electronics, Timepiece Manufacturing, Medical Equipment and Scientific Apparatus companies. Clan Rooms ensure long term reliability and safety of the products not to forget Precision.

EE Design Library – Electronic Product Design Resource.

Even if a Place is partially Dust free, it is better to have all objects with the least surface area. The way Motors are designed, Interiors of houses even a Machine

Clan Rooms and Electronics

You can enclose objects with many contours and unclean-able surfaces within a Spherical or Cubical Transparent Cover, this is easy for inspection and cleaning.

Dust, Oil, Sand and Humidity makes Grime. Never allow Rodents and Roaches in the Workplace they are larger than 100 microns.

Resources – Electronic Firms and Electronic Projects.

Tools and Equipment must be maintained free of rust/corrosion and exposure to brine or chemical fumes. Metal tools must be cleaned, oiled and stored in dry places when not in use.

Power Electronics Design Methods

I first saw this practically in the Orthodox Cherokee SMPS. This is where we differentiate from Engineered Products and just Mass Production without following standards. The Cherokee SMPS was a work of art, perfect in all respects.

The Copper Desert or Isolation Land

There is a No Man’s Land in PCB. Any good power electronics designer should/will know. Product Safety and HV Isolation, Quality and Reliability all depend on this.

High Energy Circuits

Power Electronics Design Methods

These things don’t come overnight, it is a culture, learning, experience and integrity of some of these American Firms. Reliability and Product safety are important. Every human values his life very much. A manufacturer too should appreciate this.

Coming back to isolation, Keep in mind creepage distance, High energy circuits and Low voltage circuits should have clear isolation, use the best insulation. Fire and shock hazard. Mains HV transitions, spikes.

Regulated High Voltage Power Supply

Power supply faces all these, even other areas where a Human Life or Property can be endangered.

HV High Voltage Reliability and Safety

Use a Servo Stabilizer or CVT Constant Voltage Transformer or at least an Isolation Transformer. The First Defense form HV Surges, Spikes.

High Voltage Polyester & Polypropylene Metallized Capacitors in Stepdown Supplies should be Fire Retardant & Self Healing with a MOV too.

Equipment Control using Embedded Internet

I will give a simple example for the purpose of understanding and assimilation of the concept. Consider the Toaster a Vital Home Appliance, Build a Embedded Internet Interface into the toaster. Then make it Wireless Networking capable. The gadget can also get connected thru Mains Carrier Communication.

Now you build a Webware service, create API’s, Ready Gadgets and Wizards. So he can create-use the API from any Computer or PDA. He can Sub-Lease his custom API Service with Internet capable Gadgets.

Make this a Web Toaster – When i made this post, the iGoogle was the reason behind it.

Make this a Web Toaster

When the Javascript of this is linked to the API of the Control Webapp that you created, This gadget can monitor and control the Quality of the Toast from anywhere in the world ;-).

Digital Timer for Internet – Live Widget

But Then, the service should be easy for just anyone to use, the coding is never done by the user of the service. He creates an account, hires the API, creates his own Gadgets and Apps with wizards. Then he gets to download the firmware for the Embedded Internet ASIC you Provide and the Product he manufactures goes with that circuit. See a Screenshot below


The end customer buys an Internet capable Toaster with a CD demo on how to access his free webservice. With this service, he can get all the web gadgets and tools to control his Home Appliance Arsenal.

Idea – 19:36 25-Feb-08, Nature – Open Source, – Ideas of delabs

More Reading –

Tech Ideas as Feedback – Computers

These are some ideas, comments, feedback and communication that i have had over the past many years online. 2006-11

Photonic Speeds

The real speed can be seen when we switch completely to photons and photonic circuits. No more electrons. Blazing Tera Hertz Transfer Speeds. Just a few decades away. Another smart alec comment i made at the site of a major speed provider.

System-on-Chip – SoC – IP

3D Hologram Newspaper

3D Hologram Newspaper

An Interactive 3D Hologram Newspaper that is Projected by a Small Rechargeable Pendent or Desktop Device. It can be a MultiMedia 3D Book, Magazine or Newspaper. It can be used even when lying down on a bed. It can be used on a Restaurant, the group can read the day’s Paper. (An idea i gave at a website with a Questionnaire, years ago)

Digital Signal Processing – DSP

Rechargable Wireless Peripherals

Buy only those Wireless Peripherals or Even Keyboard / Mouse, that can be recharged & dockable or on a Ferrite / Magnetic, No wire/metal charging base. (Just drumming up an old idea of mine)

Storage Tripod Hybrid for Reliability Speed

The wear and tear, fragmentation on HDD can be reduced using a Tripod Hybrid. Access Speed improves too…

Top Layer is RAM Drive with Li-ion Battery. Second layer is Flash. Third is the Spinner HDD.

All active files of user are on RAM drive and backed up on Flash by intelligent Drive (not CPU). The files go into HDD after they have been stable for over an hour. As HDD sizes are increasing. The files and file system can be like svn and maintain 3 versions of all dynamic files. This is useful for user also and HDD too.

Storage Tripod Hybrid for Reliability Speed

Static files like Binaries can be on one area of HDD. Frequently accessed binaries are promoted to flash layer. Extremely frequent to Ram Layer. The HDD now is less stressed and lasts longer and is a stable backup. Power failures immune.

Bare Essentials

A supercap built into a HDD. On Brownout OR Power Fail. The falling ramp is detected beyond an isolating diode. It says to HDD uC … Look there is something funny with power now. The HDD uC at once finishes the work at hand, drawing its juice from the stable supercap, parks its heads and goes to sleep.

When power is stable again, it wakes up and the supercap is replenished too. This way damage to HDD is avoided, these happen when .. battery connection problems in laptop or mains power fluctuations or switching power systems carelessly. It makes HDD idiot proof at least electrically.

– delabs 2009