Have a question about ADCs or DACs? Ask our Expert, Nick Gray

HI,

i have a small question that is it possible to convert radio and micro waves coming to our mobile during a call to be converted in to electricity,i am working on that please suggest me appropriate way

Hi Mukund,

I am not sure just what you want to do. I know you want to convert the radio waves coming from your mobile phone, but I do not know what you want to do with the energy once you "convert" it. If you want to decode the information coming from it, you really need the equivalent of a mobile system base station, which is a LOT of circuitry. The information transmitted in addition to the voice or text information includes a lot of things, including information needed to know when to change receive and transmit frequencies when the mobile phone leave one cell area and enters another.

If you mean convert it to electrical energy for general use, like replacing a battery or something, than that is not practical because it the energe generated is so small that it is almost completely useless.

If you mean something besides one of these, please explain just what you want to do and ask again.

Nick Gray

Hi Nick

I would like your help with the selection of a suitable ADC IC for a sensor product I am working on.

I  need to accurately read (16 bit), the analog output of 2, 5 volt hall  effect sensors, the output of which swings from 0.5 to 4.5 volts. The  output of the sensors changes very slowly over time so I don't need  anything fast. I can allow up to about 2 seconds for the conversion. My  device wakes up every hour, reads the sensors, stores the result and  then goes back to sleep.

I'm  using a PIC18F46J11 as my controller which runs at 3.3 volts but I also  have a 5 volt supply on the board to power the 2 hall sensors. I'm  using SPI for interfacing to all the other components so the ADC also  needs to be SPI.

Ideally  the ADC would be able to interface directly to the pic with 3.3v SPI  lines, but the analog side to be able to cope with the 5 volt input of  the sensors.

I know there are various types of ADC but I'm not sure which would be most suitable for this application.

Many thanks, Ben Harker

For example ADS1146 and similar:

http://www.ti.com/product/ads1146

Hi, Ben,
A couple of ADCs that should do well in your application with Hall Effect sensors are the ADS1146 and the ADS1255, both from Texas Instruments. I am sure that other suppliers probably have suitable devices as well. However, I think that it would be much less expensive and use less board area if you combined the PIC and ADC in a single package by using one of the CY8C34 family of Programmable System-on-Chip (PSoC) devices from Cypress Semiconductor. Digi-Key shows pricing at less than half of the price they show for the ADS1146 or the ADS1255, in addition to the board area and inventory cost savings. The PSoC devices can operate from supply voltages of 1.7V to 5.5V and have separate analog and digital supplies. The analog supply must be equat to or greater than the digital supply, so operating the digital at 3.3V and the analog at 5V is absolutely no problem.

The PSoC can be shut down to consume almost no power when not needed. It has an 8051 core, up to 64k of Flash memory, up to 8k of RAM, have SPI, I2C, USB and CAN interfaces, have a Delta Sigma ADC that can be programmed for resolutions of 12 to 20 bits, has timers, counters, PWM, four DACs (voltage or current output), four op-amps, four voltage comparators, sample-and-hold, temperature sensor, programmable analog blocks that can be used to build any number of analog functions, LCD direct drive circuit, CapSense inputs, up/down mixer and just about anything else you need for mixed signal systems. The PSoC Creator software allows you to configure your PSoC just the way you want to without worrying about how to make your custom internal connections. Create your schematic in the PSoC Creator software, then tell the software to configure your device. This is really a fast, easy way to go.

Hi, Ben,
A couple of ADCs that should do well in your application with Hall Effect sensors are the ADS1146 and the ADS1255, both from Texas Instruments. I am sure that other suppliers probably have suitable devices as well. However, I think that it would be much less expensive and use less board area if you combined the PIC and ADC in a single package by using one of the CY8C34 family of Programmable System-on-Chip (PSoC) devices from Cypress Semiconductor. Digi-Key shows pricing at less than half of the price they show for the ADS1146 or the ADS1255, in addition to the board area and inventory cost savings. The PSoC devices can operate from supply voltages of 1.7V to 5.5V and have separate analog and digital supplies. The analog supply must be equat to or greater than the digital supply, so operating the digital at 3.3V and the analog at 5V is absolutely no problem.

The PSoC can be shut down to consume almost no power when not needed. It has an 8051 core, up to 64k of Flash memory, up to 8k of RAM, have SPI, I2C, USB and CAN interfaces, have a Delta Sigma ADC that can be programmed for resolutions of 12 to 20 bits, has timers, counters, PWM, four DACs (voltage or current output), four op-amps, four voltage comparators, sample-and-hold, temperature sensor, programmable analog blocks that can be used to build any number of analog functions, LCD direct drive circuit, CapSense inputs, up/down mixer and just about anything else you need for mixed signal systems. The PSoC Creator software allows you to configure your PSoC just the way you want to without worrying about how to make your custom internal connections. Create your schematic in the PSoC Creator software, then tell the software to configure your device. This is really a fast, easy way to go.