Friday, April 21, 2017

How does RTD Work

How Resistance temperature detector works?

Post by JG

The most popular RTD is PT-100, Platinum 100 Ohms, As all Metals have a Temperature Coefficient of Resistance. The Resistance of RTD increases with rise in temperature.

How does RTD Work

Even Copper wire can be used, but you need to have a very thin and long wire to make usable measurements.

Resistance: Temperature Coefficient - Since the electrical resistance of a conductor such as a copper wire is dependent upon collisional proccesses within the wire, the resistance could be expected to increase with temperature since there will be more collisions

Resistance thermometer - Wikipedia - . The RTD wire is a pure material, typically platinum, nickel, or copper. The material has an accurate resistance/temperature relationship which is used to provide an indication of temperature. As RTD elements are fragile, they are often housed in protective probes.

What are RTDs? - in the case of Platinum known variously as PRTs and PRT100s, are the most popular RTD type, nearly linear over a wide range of temperatures

What is a Resistance Temperature Detector (RTD)? - Most RTD elements consist of a length of fine coiled wire wrapped around a ceramic or glass core.
The material has a predictable change in resistance as the temperature changes; it is this predictable change that is used to determine temperature.

This is an answer of mine to an old post - 2006

Thursday, April 20, 2017

Spice Simulation for CD4060

I found your web site today. I am looking for the CD4060 spice model for Orcad Capture. My Orcad version is the 9.2 (complete but without CD4060 !!)

I saw on your web pages a design using this component. How can I have the CD4060 model (to use it in simulation) ?

Mail from EG France

Try using 74HCT4060 or maybe 74HC4060

74HCT4060 or  74HC4060

Have a look at these links.

SPICE Simulation Fundamentals - Basic SPICE Simulation Model Parameters, SPICE Simulation Control Statements. SPICE Simulation Source Type and Parameters.

PSPICE Resources -  Where can I get my own copy of PSPICE using Schematics? (the student version 9.1 is free)

SPICE Resources - SPICE is available in many different "flavors." Several versions are presented below for your downloading pleasure.

SPICE - A Brief Overview - The description is far from complete, as SPICE is a powerful circuit simulator with many capabilitie

The SPICE circuit simulator and models - SPICE is an acronym for Simulation Program with Integrated Circuit Emphasis and was inspired by the need to accurately model devices used in integrated circuit design. It has now become the standard computer program for electrical and electronic simulation.

"The Orcad demonstration package includes several libraries for circuit layout, but only the EVAL.LIB has SPICE models as well. This library includes a range ...."

Please study all links above and tell me if it solves your problem, Look and study each link above. If you have a problem still, then i will search again or find a solution


Tuesday, April 04, 2017

Bioamp for muscle signals - EMG

message: I'm working an a bioamp for muscle signals. This is the base design, but it does not work. Basically what I want to do is a circuit that amplifies my muscle signals and is able to run a small dc motor when I flex a muscle. Any help? Thanks

Mail from JX US

Electromyography (EMG)  - An electromyograph detects the electric potential generated by muscle cells. when these cells are electrically or neurologically activated.

Electromyography EMG

Study these links and send me a feedback ....

Positive Feedback Circuit for Isometric Muscle Experiments - he part of which I am most proud is the innovative Automatic Gain Control (AGC) circuit, without which the project would not have succeeded. This AGC circuit could well be used in many other applications too

EMG design parameters - The device must be able to detect the small signals arising from muscular contraction and amplify them without also amplifying ambient noise which may exist in the recording environment and which is likely to be of approximately the same magnitude as the signals of interest.

Important Factors in Surface EMG Measurement - Small electrical currents are generated by muscle fibres prior to the production of muscle force. These currents are generated by the exchange of ions across muscle fibre membranes, a part of the signaling process for the muscle fibres to contract. The signal called the electromyogram (EMG) can be measured by applying conductive elements or
electrodes to the skin surface, or invasively within the muscle


Sunday, March 19, 2017

Coffee maker PID Temperature Control

My name is RP  i'm working on a project to regulated the temperature of a coffee maker. I don''t know were to start. what i want is to regulate the temperature of the coffee. Could you please help me.

Mail from RP

This is what you may have to do. study below pages and try.

Murph's Silvia PID Page - This page describes my effort to improve temperature control in a home espresso machine by installing a PID temperature controller. If you are reading this page, then you probably already know what Silvia is, what PID means and why anyone would want to add one to the other.

Coffee maker PID Temperature Control

Tuning a PID (Three-Mode) Controller - . If the controller does not include an autotune algorithm or the autotune algorithm does not provide adequate control for the particular application, the unit must then be tuned using a trial and error method.

PID controller - Wikipedia - A PID controller continuously calculates an error value {\displaystyle e(t)} e(t) as the difference between a desired setpoint and a measured process variable and applies a correction based on proportional, integral, and derivative terms.

Temperature Control - PID and LabVIEW - First, let's take a look at how the PID controller works in a closed-loop system using the schematic shown above. The variable (e) represents the tracking error, the difference between the desired input value (R) and the actual output (T). This error signal (e) is sent to the PID controller.


Saturday, March 18, 2017

Halogen bulb lamp dimmer circuit

Can someone provide me a (simple) schematic for a dimmer that would control 12 VAC about 80 watts. This would be used to control a lamp with halogen bulbs.

A comment in Hobby Hound

Here is a listing study them and choose, try out, learn and then build the one right for you.

1200 Watt Lamp Dimmer Circuit The following circuit is a lamp dimmer circuit that is capable of controlling up to 1200 Watts. The circuit uses the Q4015LT combination Diac and Triac that is available from Digikey Electronics.

PWM Motor Speed Controller / DC Light Dimmer - Here is a listing study them and choose, try out, learn and then build the one right for you.

DC Controlled Dimmer Velleman kit - K8064

Halogen bulb lamp dimmer circuit

Simple brightness adjustment by means of a DC voltage, optically isolated adjustment input. Pre-set adjustment for full brightness, suitable for incandescent lamps, mains voltage halogen lighting and low voltage halogen lighting in combination with a conventional transformer. "Soft start" feature to ensure lamp longevity, transformer protection in case of defective light sources

Electronic Transformer for 12V Halogen Lamp - STMicro
The topology of the circuit is the classic half-bridge. The control circuit could be realised using an IC (so fixing the operating frequency), but there is a more economical solution which consists of a selfoscillating circuit where the two transistors are driven in opposing phase by feedback from the output circuit.


Friday, March 17, 2017

How to Connect RTD to transmitter

Can you explain me were i have to conect the three cables of the PT100 in the Circuit RTD-Pt-100-Transmitter Circuit?

RTD PT100 Transmitter and Multiplexer

Comment from CV of Spain

You have a three wire RTD, there is also a 4 wire RTD type, This circuit can be used for both.

In the 3W RTD you have two wires coming from the same point (zero ohms between them) the third wire will be 100 ohms from these two. From the two wires that are at same point take one wire and give 1mA from Q3 + OUT. The other wire of the pair connect to input +..... input - can be connected to the 100E end.

How to Connect RTD to transmitter

So imagine that I have three wires one white and two blacks.

One black to +OUT 1ma
Other black to input-

And waht about the withe one that is the one that give me arround 100ohms??

Reply from CV

Black 1 - +Out 1mA
Black 2 - +Input
White goes to -Input

See NI Developer Zone - RTD Connections


Saturday, February 11, 2017

Battery Management and Supply Design

As you have have pointed out, my circuit is not driving any motor or such loads...but it is driving a Wireless Module which draws about 165mA to 240mA from my circuit during transmission [for 4 sec] and normally it takes upto 114mA. After a time-out of 1min, I put my uC P89V51RD2 to powerdown mode [200uA in this state].

Read articles in the link you provided, thanks for that! - Continued from uC Board is Misbehaving on Brown Out.

My other problem is that my batteries get supercharged upto 5.8V, and as per spec's of most IC' they are bound to operate faithfully upto 5.25[max 5.5v], so how do I solve this issue? I want that my boards get only 5.25v even if my battery is having voltages 5.25+, without increasing my existing current consumption to noticeable value.

Moreover I'm in need of a cutt-off circuit which will take away the load from my batteries when my battery has reached 4.00V, & the charger charges my battery independently. Do you have any thing which will suite my purpose?

Mail from MO

Have two supplies, the one for uC can be a small Ni-Cad battery charged by a diode by the bigger battery which supplies the 200mA for RF drivers.

So when the big battery is loaded and the supply dips the shock is not felt by uC. or isolate it by SMPS and isolate the grounds. The ground return current of RF module 200mA must be lifting the ground of uC or some Logic.

Start by trying to locate the problem, first power RF and uC boards with isolated lines from two lab-test 10A power supplies. If both are in same board, cut tracks and power them separately. The grounds should meet at point the two sections interface.

If that works without problem, you know it is related to supply, now step-by-step go back to the battery and charger you have built keeping isolation intact. Look for spikes-glitches on power lines of uF when RF module active. Check if that is close to or leaking RF to uC circuits.

The battery charger circuit should limit voltage and current to battery specs. If you are not using a charger chip then while testing make sure the charger has a regulator or use LM317 to clamp voltage to 5.6 or 5.5 as per your design.

There are charger chips from maxim, national for battery charge management. If you have a need for extra voltage the you have to use SMPS boost switcher. which may take the low battery 4 to 8 which can be regulated to 5 using 7805.

This may be getting bit complex, first try to find what is the problem, it may be just the board design.

Battery Management and Supply Design

You can also use a Single Maxim Chip for all these functions. ...

Supervisor ICs Monitor Battery-Powered Equipment

A feature-laden µP supervisor (IC1), with the help of the µP itself, performs a variety of functions in this typical application circuit. You can get these functions all together or in various combinations, by selecting one of the many available microprocessor (µP) supervisor IC....