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Electronics => Projects, Designs, and Technical Stuff => Topic started by: rickey1990 on January 27, 2016, 01:00:13 am

Title: Circuit rendition - thanks for the advice.
Post by: rickey1990 on January 27, 2016, 01:00:13 am

My project update, I have posted a few renditions of the board, took some advice from here and I have also been talking to a few volunteers at hobbyist groups in the UK, Lots of different age ranges with different preferences regarding microcontrollers, Pic, atmega's, 8051's, Also I have been speaking to a few people who are not electronics enthusiasts but want to jump on the band wagon. Im trying to keep the board as modular as possible,but not cluttered. This is because the person will have to make physical connections between the inputs and outputs of each module with jumper leads. I am also currently developing a website, With information on each section of the board, explaining how it functions and its layout. Starting off simple and increasing in complexity. There are also calculators for the working out of resistor values.

A few people have asked me about the cost, my budget for the project is £300 ($430) This will cover the design costs,great chap in sri lanka does my work. The printing of 100 boards and all the components from china for those 100 boards.

My changes are, instead of a VGA port, there will be a SD card interface with support circuitry (up to 2gb). A oscillator circuit, A reset circuit for PICS & ATMEGA'S, but can be modified to work with 8051's. The outputs of the max232 is left unconnected so Bluetooth and wifi devices can be used along with the two rs232 ports. Space for filter capacitors. Additional + & - pins. A RGB led, mounting holes. small prototyping are and space for icsp/10pin jtag.

I am hoping to sell the kits for £25. Including jumper wires,Choice of microcontroller, RGB led, All the headers, Max232, 2 rs232's,SD card slot pretty much everything except the SD card and power supply.

(http://3.bp.blogspot.com/-wMV6NxlpR9o/VqgDEu-0vlI/AAAAAAAADZk/VZ5I070JCmU/s1600/Circuitsexamples.png)

(http://3.bp.blogspot.com/-UcFLZNC4ROk/VqgD6vLDE3I/AAAAAAAADZ0/pCGvbRo-8g4/s1600/resetswitch.png)

Title: Re: Circuit rendition - thanks for the advice.
Post by: LukeW on January 27, 2016, 03:06:58 am

Why are you using an RS-232 connection to the PC in 2016? Many people would struggle to find a computer with an RS-232 port.

Using resistive dividers for the SD card is a bit rough... it can work at low speeds, depending on the input and output impedances and the parasitic capacitance on the SPI lines, but using an IC is better.
Or, better still, just run the microcontroller at 3.3V logic levels with nothing to translate.