Processor Board Project using a PICAX-40X1

[oldjoe]

This project provides a socket for a PICAXE-40 that can be programmed with Revelation’s BASIC Editor/Compiler/Programmer/Simulator/System-Monitor/Debugger. This Project also has provisions for several passives and has sockets for other useful IC. See photo.

This Project is small, light and cheap and is tailored for a PICAXE-40X1. It is about the size of a credit card, it weights about an ounce and this project has an initial cost of under $40US which includes the PWB ($20), the 7805, PICAXE-40X1, Ceramic Resonator and all the rest of the discretes. Actual Size: 3.8” X 2.5”.

The schematic is nothing special, it is the chaining together of several Vendor Application Notes, the PWB Artwork is unique and I put it in the Public Domain for anyone that wants to copy it.

This project also provides sockets for eight I2C Memory chips, plus one other I2C socket that can be used for a Real Time Clock and a socket for a +/- 10V Charge Pump that can be an up to a 100 ma power supply for other things. The I2C and One-Wire lines are taken to the I/O Board.

Parts List for PICAXE Processor Board Version G:
C1 10UU@50VWDC Jameco 852473 or Radio Shack # 27-1025
C2 .001U@50WVDC Jameco 15192 or Radio Shack # 27-210126
C3 0.01U@35WVDC Jameco 15231 or Radio Shack # 27-21065
C4 22U@35WVDC Jameco 545887 or Radio Shack # 27-21026
*C5 0.1U@35WVDC Jameco 545561 or Radio Shack # 27-21069
*C6 22U@35WVDC or any value above 1U Jameco 545561 or Radio Shack # 27-21026
*C7 22U@35WVDC or any value above 1U Jameco 545561 or Radio Shack # 27-21026
C8 0.01U@35WVDC Jameco 15231 or Radio Shack # 27-21065
C9 0.01U@35WVDC Jameco 15231 or Radio Shack # 27-21065
C10 0.01U@35WVDC Jameco 15231 or Radio Shack # 27-21065
*C11 22U@35WVDC or any value above 1U Jameco 545561 or Radio Shack # 27-21026
*C12 22U@35WVDC or any value above 1U Jameco 545561 or Radio Shack # 27-21026
*C13 1F@5VDC Jameco 227811 used only by the DS1307.
D1 RED LED Radio Shack #27-60041
D2 IN5819 (DO-41 case) Schottky, 40V 1A Digikey #1N5819-E3/STGI-ND
D3 1N4007 (DO-41 case) any power rectifier diode will do, as long as it fits and PIV is OK.
*D4 1N4148 Jameco 36038
DIP-8 Jameco 112206 order enough for locations U2 thru U13.
DIP-8 Oscillator Socket Jameco 676385 can be used in location U13.
DIP-40 Jameco 112311 for location U14.
JP1 3.5mm Stereo female connector Mouser # 806-STX-3500-3C, check foot print.
PWB1 order from EXPRESSPCB
R1 10 K 1/8W 5% Radio Shack 27-11126
R2 22 K 1/8W 5% Radio Shack 27-11128
R3 4.7 K 1/8W 5% Radio Shack 27-11113
R4 330 1/8W 5% Radio Shack 27-11215
R5 180 1/8W 5% Radio Shack 27-11205
*R6 47 K 1/8W 5% Radio Shack 27-11130
*R7 47 K 1/8W 5% Radio Shack 27-11130
*R9 330 1/8W 5% Radio Shack 27-11215
RN1 10 KX10 SIP Jameco 280947
RN2 10 KX10 SIP Jameco 280947
SW1 Push Button Switch NO, Jameco 122973, check foot print.
U1 LM7805 Jameco 786138 or Radio Shack 276-1770
*U3 MAX680 charge pump, +5 to +/-10V Converter
*U4 any I2C memory chip, sockets are hardwired for address extension
sockets are hardwired for either 24FC256, or 24FC512 or 24FC1024.
*U12 any I2C Real Time Clock, socket wired for DS1307
*U13 TTL Crystal Clock Oscillator 30ppm stability, Mouser 520-TCH400-C
U14 PICAXE-40X1 (Enhanced) sales@hvwtech.com or www.microchip.com
X1 4MHz ceramic resonator, Jameco 324697CJ or www.microchip.com
*X2 32.768 Crystal to go with DS1307, Jameco 14584
JP2 RC battery Connector Repair Kit Radio Shack #23-00444, solder the male half to PWB and use female half of this kit for the Wall-Wart power supply.

Programming Cable Any NULL-MODEM cable cut in half and each half along with male 3.5mm Stereo connector makes a programming cable, see schematic for connections.

*I/O Cable Any 50 conductor ribbon cable. Moser 3365/50 .

* indicates item not used on initial project, but PWB is ready to take these components

How to build this PICAXE Project: Download the free software from www.expresspcb.com ; you will need this software to view my schematic and my artwork files as I designed them using this software. Print out the parts list and buy three copies of each part, wait for the parts to come in before ordering the printed wiring board, as you need to double check the part’s foot print against the PWB. When all is OK, order the PWB. Any questions then e-mail me at: bigjoe@valp.net .

Stuff the PWB and solder. For this project U1 is soldered-in, and the PICAXE-40X1 is inserted into U14 socket, the rest of the IC Sockets are reserved for future projects.

How I soldered: Let me tell you how I had to solder this project to make it work, it might save you a wasted board. Everything on this PWB is small and jammed together; the fabrication of this Board is at the high end of the expected Hobbyist Soldering Skill level. Soldering all of these 8-pin DIP sockets is very tiring and frustrating, just one solder blob or bridge will ruin everything, and there are no provisions for re-work. Due to the close spacing on some of the DIP sockets there is a requirement for order of assembly. Here is what I found I had to do to get things to work: insert the sockets for U4, U5 then solder; U6, U7 and U8 then solder; U9 and U10 then solder; U11 and U12 then solder. The rest are easier. I found that I needed to use a bright light and 6X magnifier to see to solder; also a pencil iron with a narrow conical tip, a 0.020 (or 1/32) tip and some 0.031 thin multi-core rosin solder to do this job.

My design philosophy: Put all hardware parts that are not going to change from project to project on the Processor Board. Put anything else on the Interface Board. This PICAXE Project is the Processor Board; from project to project nothing will change further on this PWB, except seating some IC into their sockets and the loading of new software.

Power All the power is conditioned on the Processor Board and pass from this board to the other boards via the 50 pin ribbon cable.

Programming I put all the components for the programming circuit on this processor board. So to build your own Programming Cable: 1) buy any Null-Modem Cable and 2) cut it in half. 3) On the cut end, bear the wire that is connected to pin 5 on the female DB-9 connector and solder this to the shell of the 3.5mm male stereo connector. 4) Same with DB-9 pin 2 to 3.5mm pin 2 and DB-9 pin 3 to 3.5mm pin 1. Also see the schematic for wiring diagram.

Ups and Downs I use RN1 to pull-down all the PICAXE-40’s ADC pins, this helps reduce noise and I use RN2 to pull-up the Input Pins. If this is not the way you do things, then leave RN1 or RN2 off the board. I use the ADC for analog sensors and I put Op-Amps on the I/O Board for signal conditioning. I use the PICAXE’s Input pins for Digital or Microswitch inputs; the input logical signal will be HIGH with no switch action and with a switch closure, the pin connected to the switch will go LOW for a brief instant. See the PICAXE Users Manual, Section 3, for designing sensor circuits, more in the next project.

Clock Decision: Often, Advanced Micros will give away a free Ceramic Resonator with the purchase of the PICAXE-40. The Ceramic Resonator is great at keeping cost down. But when I am doing Digital Signal Processing or Digital Signal Synthesis, the stability of a Ceramic Resonator is not good enough, so U13 is provided for a crystal oscillator. For DSP, 10ppm or better is desirable; 30ppm is useable; anything above 100ppm will cause problems.

Future: There are a lot of 8-pin DIP sockets on this PWB reserved for future projects. For example U4 thru U11 could be populated with 24FC256 I2C Memory chips for over a Gig of external memory, the I2C address extensions are already hard wired to these sockets. U12 is wired for any I2C chip like a DS1307 Real Time Clock that could be used to time stamp data and all that Memory could be used as a data logger. For a Data Logger, the signal conditioning and cable connectors would be on a separate board which connects to this Processor Board with a 50-pin Ribbon Cable. All the PICAXE-40 I/O pins are brought to the I/O Board so there are lots of I/O pins for the sensor channels. Think Robotics, PID Closed-loop Servos, Factory Automation, MIDI Music, for future projects. With so many I/O pins on the PICAXE-40 the possibilities are very many.

See attachments for schematic and artwork for PWB. You have to rename them to make them work:

ProcessorG1.dsn -> ProcessorG1.sch
ProcessorG2.dsn -> ProcessorG2.pcb

Then open these files with espresspcb.exe

This post has been modified, the schematic, artwork and photos have been moved to another post.

 

[BeanieBots]

Might be a good idea to explain what it actually does in the first paragraph.

 

[BeanieBots]

So, it's a 40X/1 "Project Board" which includes a 5v volt regulator and sockets for I2C RAM and/or DS1307 RTC chip. Ideal for a data logger.

How many channels?

Add another post if you want more attachments.

 

[oldjoe]

Processor Board using a PICAXE-40X1

This provide the schematic and PWB artwork, the photo of the finished project is in the next post. Any questions, post to this thread and I will answer.

Don't forget to change the extensions after you download these files!!!
These files can only be viewed with expresspcb.exe free software from Express PCB.
G1 is the schematic which is nothing special, G2 is the PWB Artwork.

oldjoe

BTW, I notice that more Forum members are viewing the schematic and few are viewing the PWB artwork ... the schematic is not much the artwork is where it is at

 

[oldjoe]

Processor Board for PICAXE-40X1

This is the latest picture. Possible my problem is that these pictures are beyond the allowed limit for .jpg files .....

So the attached file is a .jpg ... just download it and change the extension.

oldjoe

 

[lbenson]

Nice design. I like the expressPCB programs and services. But too bad you can't put out Gerber files or generic schematic--they want to tie you in.

Did you mean for the attached thumbnail and dsn file to be the same?

 

[oldjoe]

Reply to Iberson's post

Thanks Ibenson

And yes, the thumbnail and the .dsn are the same picture, I am still learning how to post things to the Forum.


I like Expresspcb as well, obviously since I use it so much. It is fast and cheap and very convient. I do the schematic first, (the schematic has some error checking). Then I do the PWB Art Work, Expresspcb does not have autorouting, but if the user links the schematic to the art work; then, when one selects a pad all the pads that need to be connected together will light up and if there are any problems Expresspcb will tell you the art work is not like the schematic.

When I am done with the art work, there is a button on the tool bar to buy the PWB. I click the button and in a couple of days the three PWB arrive in the mail. $51US plus postage for 3 PWB or about $20US per PWB for me.

I am locked in, but other PICAXE users do not have to be .... Expresspcb has an export feature in the file menu on the tool bar. If anyone wants me to, I will provide these generic files, so that they can go elsewhere to have this PWB made......

Ten years ago, I made my own PWB, but I can not do it any more, the world has changed too much. Look at the photo on the prior post see how sharp the traces are on the bare PWB? When I made my own PWB, the smallest trace I could do was 0.025 and I had to maintaine 0.025 spacing from trace to pad, else there would be etching problems. Now, ExpressPCB has good production machinery, with them I have no trouble doing .012 trace for analog and .010 trace for digital and I can get 2 digital traces between the pads of a DIP Socket. I could not do that on my PWB On this project, the traces are sometimes only .010 from pads; no wonder this project is a soldering problem Also there are 350 drill holes on this PWB and Expresspcb appears to hold them to within +/- .001" . Expresspcb does plated-thru holes and I did not, nor could I drill all these holes to this tolerance.

BTW, ExpressPCB software supports surface mount, lots of footprints in their library. I use thru-hole; because, as of today I do not think the average hobbyest is set up for soldering surface-mount.

Oldjoe

 

[oldjoe]

Prototype Board Companion for 40-pin Processor Board

This is another miscellaneous project that does not do anything.

What is it … it is the companion “prototype” area that goes with the PICAXE-40 Processor Project that is posted here.

What good is it? Well right now this is the only thing that will socket and program the 40-pin PICAXE.

What is this in particular? It is a Wire-Wrap Prototype area. Why Wire-Wrap? That is such old technology! Well if one is using this combination of PICAXE Processor Board and Prototype Board to proof a design in the field, like in a DARPA Challenge type environment, then only a Wire-Wrap Prototype board will endure. I have had a similar design last 30 years in a DARPA Challenge type environment without failure. The Push-On Prototype Boards are intended for more benign service. Also note that all prototype boards are much heavier and take up more room than a dedicated PWB that does the same thing.

For the student and educator: forget this design, it is not for you.

For the hobbyist: Do not buy more than two of these Wire-Wrap Prototype Boards they are four times the cost of doing a Dedicated PWB. They only make sense if they are used to test complicated design in the field that would save the cost of scrapping a dedicated PWB with an error on it.

For the Engineer: Buy lots of these Wire-Wrap Prototype Boards they are for you. If you are a good wire-wrapper, then it will take very little time to correct an Engineering-Oversight or compensate for an unknown-unknown in the unit under test (UUT). For UUT’s, a field test program usually takes a year and costs more than $million. If a LRU is replaced, then the test has to be restarted. If only a repair is made to a LRU, then testing can continue on schedule. So for the Design Engineer, it is possible to verify the change in the lab, take any components, a battery powered soldering iron and ones wire-wrapping tool to the field, open the robot make the change and close it back up before the Test Team can finish their coffee-break

What does it look like: see attached photos: