Thursday, May 05, 2016

Long Duration Linear Sweep or Ramp Generator

I hope you can help me with a circuit. Its a voltage sweep circuit that will sweep from 0v to10v in a 45 min time period, I'm using it for an input on a signal generator to control the output frequency.

I have tried a constant current source charging a capacitor but it just didn't seem to be solid. If It can be done digitally would be great! I have been struggling to do this and its the last part of the piece for my project.

Mail from CB in NA

I have once answered a similar question. Ramp Generator Elex Quna.

You need clock pulses driving a counter, which operate a digital potentiometer. Or any D-A convector - or R-2R circuit. Say you need 1-10V in 45 mts. You first figure how fine the ramp needs to be, like resolution of 100mV?

The constant current may not work as the capacitor may leak and it may not be a perfect ramp. The cc ramp is good for 1 second or less.

A staircase ladder ramp is best for you, define every step of ladder as say 10 or 100mV. A clock of 1 Sec is given to a counter, binary counts, and the digital output of counter goes to D/A Convertor.

Another here with LTspice, install and launch  LTC6993-2 Demo Circuit to try.

 Pulse Staircase Ramp Generator
"This design highlights the use of the LTC6993-2 and LT1490 to generate a pulse staircase ramp that is re-triggerable. "

Pulse Staircase Ramp Generator

If you wish to use a PIC, AVR or 8051 uC, then use it to time and control a built in D-A convertor or PWM. This is done in the code or firmware.

So .... clock >> counter >> digital to analog >> Ramp = you got it. You can implement in both software or hardware, it is your choice.


Wednesday, May 04, 2016

Make an Encoder for your Bot

I want to build a cheap wheel encoder by myself. - Need some help here. I want to build a cheap wheel encoder by myself. Now, my idea was to use a photodiode and a LED. What i don't know is how to use the output from photodiode to put on a GPIO on my MCU board. Do i need some resistors or something. Aaaa, i need a high level of 5V for my GPIO. I - AV

Answer - Please study Links Below

Optical Encoder Project - "Many years ago, I competed in MASLab, an MIT competition to build an autonomous robot. A year or two after that, I was on the MASLab staff, helping prepare the hardware for the year's competition. One of the projects I worked on was an optical encoder."

About Encoders and How to Make an Encoder Wheel

"A typical encoder uses optical sensor(s), a moving mechanical component, and a special reflector to provide a series of electrical pulses to your microcontroller. These pulses can be used as part of a PID feedback control system to determine translation distance, rotational velocity, and/or angle of a moving robot or robot part."

Make your own rotary encoder

Make an Encoder for your Bot

"In the first and second post of this series you saw the basics of how to use photointerrupters. Now it’s time for practice. We make a rotary encoder. Here we take a single photointerrupter that gives us the pulses we can count."

Make Your Own Encoders chat - "I'm starting a·dedicated·thread on the specific encoders I used on my Homebuilt platform. I had great results. A word about the encoder disks: they must be mounted PERFECTLY to achieve consistency. Perfectly flat, true, and concentric.

Incremental Optical Encoders

Here is a method for making an encoder with two sensors for your application. If you only need speed sensing, you may want to skip down to the construction section. The important variables are the radius of the circle (r), the distance between the two optical sensors (s), and the number of divisions in the wheel (d). .....

Ananth -

Use a photointerrupters, even from an old wheel mouse if you want or build one. Then you need a Wheel with stripes and a Schmitt Trigger Gate or Comparator

A rotary encoder, also called a shaft encoder, is an electro-mechanical device that converts the angular position or motion of a shaft or axle to an analog or digital code.

Monday, May 02, 2016

Piezo Power Shoes with LEDs

Walking is a Source of Energy that can be Harvested to Power LEDs or Wearables. It may one day Recharge your Smartphone or tablet. Just start running when the Battery goes low on your Phone. -

A question in the G+ Community lead to a study of resources in the web for this college project.

Here is the first page that will interest you - Parasitic Power Shoes Project

Energy Harvesting in Shoes for Small Devices

"environmental energy sources can begin to replace batteries in certain wearable subsystems. In this spirit, this effort has examined devices that can be built into a shoe, (where excess energy is readily harvested) and used for generating electrical power "parasitically" while walking."

Goal: To develop a rugged piezoelectric shoe insert and complementary conditioning electronics for unobtrusive, parasitic harvesting of the compression energy normally lost while walking

See also Energy Scavenging with Shoe-mounted Piezoelectrics

"Abstract of pdf below — Much energy harvesting research has been conducted with ceramic based piezoelectric transducers on account of their relatively large electrical response to mechanical excitation. However, notwithstanding their comparatively low piezoelectric coefficients, piezoelectric polymers too hold promise as energy harvesting materials due to their flexibility and strength which make them ideal candidates for use in more diverse applications. "

Piezoelectric Energy Scavenging In Shoes

"The energy harvester devices are capable of capturing environmental energy and supplanting the battery in a stand-alone module, or working along with the battery to extend substantially its life. Vibration is considered one of the most high power and efficient among other ambient energy sources, such as a solar energy and temperature difference."

Development Of Energy Harvesting Source From Piezoelectric Shoe

Piezoelectric materials (PZT) can be used as mechanisms to transfer ambient vibrations into electrical energy that can be stored and used to power other devices. With the recent surge of micro scale devices, PZT power generation can provide a conventional alternative to traditional power sources used to operate certain types of sensors/actuators, telemetry, and MEMS devices.

Power Walking - STAB Resources

"i started by looking at the self-powered shoe from Responsive Environments group and wanted to acquire a large piece of piezo film that could be embedded in the sole of a shoe. After consulting with Mark Feldmeier, I learned that the piezo elements large enough to generate enough power for the shoe would be too expensive to use if I wanted to make more than just a single prototype."

Piezo-Powered Self-Lighting Circuit