From Open Circuits
Aloha from Honolulu, I found Open Circuits on or about May 15, 2007. I was searching the internet for "electronic breadboard" and found SparkFun Electronics which has a link to Open Circuits.
I have an idea for some "building block" circuit boards that engineers and students can use for breadboarding. I just happen to need something like this myself, so maybe others can use them too. I couldn't find anything like I have in mind, so perhaps there is a market waitng to be created. I'd be happy to share the scematics and artwork (once they exist) and hope that others will share their ideas. Eventualy we could build a library of these that colleges and tech schools would use.
So that is how I came to Open Circuits. It also happened to be at a time when I had just completed a project that had been hanging fire for several years. That is the artwork for some voltage regulator boards based on the LM723 IC. I have used these in several personal projects and also in some professional ones.
My main gig here in Honolulu has been the installation and servicing of recording studios. I've been at it for the past 20 years. I had one client whose console power supply needed help. The voltage regulators were a high current (7 amp) device in a TO3 package. There was one each for the +15V and -15V rails. I'd replaced them once before, but this time I could not find the devices. (I forgot what the part number was.) So I decided to use a couple of LM723s which I had a large supply of (courtesy of another project that had not gotten off the ground). I used a 2N3055 transistor as the external series pass element for the positive side and tried to use its compliment 2N2955 for the negative side. But I found I could not get the current required. I switched to a Darlington device and the problem went away, so I used a complimentary pair of 15 amp Darlington transistors in TO3 packages. The unit has now been working for nearly 10 years. I plan to share these designs here once I have a better understanding of how to upload files and what formats to use.
My other interests are in embedded processors and computer programming. I used to do a lot with Pascal and Assembly back in the DOS days. I started with Turbo Pascal 3 and Turbo Assembler, I went up to Turbo Pascal version 7 before Windows came along and made it more complicated. I started to learn C++, but got out of programming for several years. I got back into it again when embedded devices started to proliferate. I brushed off my C++, but find I'm mostly using plain C with these things. That and Assembly when something needs to go as fast as it can.
I'll continue with this as time allows.
RAF 17:45, 18 May 2007 (PDT)
Hello again, I fiished my article as well as another article I want to include. The second is not mine, but is so old I can't find it anywhere, but for the copy I have in my files. The title is: "The Many-Talented 723" and the author is Glenn Prescott. I've searched the web without finding any reference to it. I have a xerox copy from the mid 1980s. Not a very good copy, but I scanned it and ran an OCR program on it. I still had to do a lot of editing to help out the OCR. Then I had to do all the images over again myself. I kept them as close to the originals as I could, except for scale, mine are a little larger and this more legible. My text is also full page instead of the 4 column format of the original. So now I'm ready to put this all together. I uploaded a symbol for the image of the 723. Otherwise it would be a picture of a 14-pin DIP. I'm going to see if I can copy it to this page...
OK, that wasn't too bad, except for forgetting what the name was... Now let's see about the Component article. RAF
Well, I had to write the question to David Cary. I couldn't figure out how to make a stand-alone article for the 723. What I did was put it in the "discussion page for the image file. That is just a temporary solution and there isn't any room for my in-depth text on using the 723 anfd Glenn Prescott's article "The Many-Talented 723". Hopefully David can show me how to make it happen and all will be well...
I figured out how to post a new article. I searched for "New Article" and of course the search returned with "no such thing found", but it has "thing" in red. Aha! it is an internal link. Click on it and it takes you to another page that says basically "Hi this is not the page of "thing" because "thing" does not exist. If you would like to create "thing" click on the edit button. So I did and was able to copy/paste my article and save it.
For anyone who was holding their breath waiting for my promised articles, here is a link to the first:
The second has been up for a while:
And I just uploaded some schematics to it, so if anyone was wondering how to hook some of these up, here's a clue or two. (Hint: go to "My Experience With The 723" for the links) I have some others still to go and then there are some Printed Circuit designs that go with these schematics, I have a little more work to finish them, but they will get here.
I've been working on a metering instrument that needs a graphic LCD for the display. I've decided to share my experience making the display with Open Circuits. I just received the unit, so I'm excited about it. I'll start working on the design over the weekend. The unit needs an inverter for the CCF lamps and a controller to provide an interface between the display and a micro. I'll get the project started and open it up for ideas.
--RAF 00:10, 20 June 2007 (PDT)
Update on What's Happening
Here is an update. Nobody responded to any of my emails asking what inverter will work with the LCD I purchased. The unit is a Sharp LM32C04P 320x240 Color LCD Display. The color is one bit each RGB, so a total of eight colors including black and white are possible. It needs an inverter and a controller. I was able to get a hold of a specifications data sheet showing all the signals and timing requirements. This has enough information to design a controller circuit and if I must, an inverter as well. However, I think I will purchase an inverter once my funds recover. I have already completed a couple of schematics for a controller circuit using a 32K x 8 SRAM and a counter, so the MCU can concentrate on loading the SRAM with data to display and the counter will do the drudge work of stepping through the addresses and sending the data to the LCD bus. The MCU will also have to talk to whatever device is using the display. So I have to figure out how to make it be an interface as well. For the controller I decided to try using Microchip's 16-bit family of devices and purchased an MPLAB ICD2 and 16-Bit 28-Pin Starter Development Board. I am currently working my way through the demo code and data sheets, to get an understanding of both the devices and the tools. One won't work without the other and there is always at least a 6-week learning curve (for me) before I'm confident enough to work without the references open beside me. Just when it seemed like progress was going to be swift and sure, my mother and brother and family decided to sell the family house and move to the big island. I will have to find another place to live and my sights are turning towards Orlando Florida. I have friends there and it looks like there is work for electronics engineers there. So my life is going to be going through a bit of upheaval until I get moved and setteled in somewhere. I'm going to try to continue my studies with the Microchip devices, so I won't be starting up again from scratch. I hope to be able to drop in here now and then over the next 3 months or so, but it will probably take at least that long to get setteled in at a new place. Meanwhile if anyone has any ideas, suggestions, or questions, post them here and I'll try to check in often enough to give a timely response.
RAF 19:56, 4 July 2007 (PDT)