Do's and Dont's of a PICAXE

Here are some notes that may keep you from 'frying' a PICAXE!

1.  NEVER supply a voltage over +5.5VDC, not even +5.6VDC, to a PICAXE!!
     The closest you can get, is to use rechargeable--  Four AAs, out
put +4.8VDC,
     whereas Four standard AAs will out
put +5.2VDC or greater.  If a power supply
     is used, it's output should be set to +5.0VDC via Voltage Regulator.

2.  Manual #1 on page #8 shows the typical setup between the PICAXE and the,
     (USB or Serial cable) that plugs into a 3.5mm Jack mounted on your project board.
    Their are two resistors, 22k & 10k that make up the network going to the Serial-In
    Leg of the PICAXE.    

    NOTE: AXE026 is the Serial Cable.  It doesn't always work due to the levels com-
                  ing in and out of the Serial Port!  Sparkfun carries a board that will fix this
                  problem.  The newer Laptops seem to have this problem the most.

    NOTE: People overseas tend to do the opposite of us in the USA.  A 3-pin Stereo
                 3.5mm Jack in general, has the larger band nearest to the connector/cable
                 is always Ground.  But Europeans, (and the company that make the
                 AXE027 USB cable), have the Tip, (at the end of the connector) as ground. 
                 Go figure!  Isn't it FUN to compare notes-- YAWN? 

 The following is a screen shot of my enhanced version for the Programmer / interface.
My circuit leaves out four parts for each project you need to program. You will only need
one resistor and a shunt-jumper after the Programing Cable is removed.


3.  In manual #1, see diagram on page #45 for an advanced setup for programing a
     PICAXE.  This is much more stable then the circuit on page #8.  I will keep this
     page up to date; the 3 manual's have also been updated.  The new 18M2, 14M2,
     20M2 and the 08M2 chip's has been released and have some new commands.
     Manual #1 & #2 have been updated, again to reflect these changes:  July 2011.

4.  If you remove the program cable from your project, make sure, (if you have a
     PICAXE that has a "Reset" line), to place a 4.7k resistor between +5VDC and
     the Reset line.  Leaving it "floating" may give unknown results.  If you don't
     have a 4.7k Resistor, you may substitute with a Resistor value up to 10k.  This
     is not true for the 08M & 14M.  There is no Reset line.  Power-OFF, wait a
     couple of seconds, turn it back ON, this will  put you back in business. You
     can always re-download the code as well.  If it still does not reset the 08M
     or 14M, then pull the power cable to your project, start the download, then
     apply power once again to your project. The has always worked for me.

5.  Please note that the 28X2 and the 40X2 Power Legs handle any voltage
     between +2.1VDC and 5.5VDC.  This is also true of the M2 class of PICAXE.


Here is a Quick list of what you will find in Manual #3

 Page   6 - EMF and how to get around it.

 Page   7, 16 - ULN2003(A) 16-Pin, ULN2803(A) 18-Pin.  Darlington Drivers.

Page   8, 12 - Using IRF5xx or IRL5xx components to drive a Motor.

Page   8, 14 - Interfacing to a Relay.

Page   9 - Driving LEDs.

Page  10 - Driving a Light Bulb or Buzzer.

Page 11 - Piezo Sounder or 40Ω Speaker.  Caveat: A 
10uF Electrolytic
connects to a Speaker.  The "+" side of the Capaci-
                tor goes to the OUT PIN of the PICAXE. The negative side
                of the Capacitor goes to the "+" side of the Speaker, and the
                "-" side of the Speaker goes to Ground.  

Page 12 - A Solar Motor, (or a Toy Motor in general), should have
                a .22uF Capacitor across the solder lugs of the Motor.

Page 13, 18 - Using an L293D, (or L393), are used to drive 2-motor circuits.
                      They take care of the higher current that these motor's demand.
                      (Info on the L298 should be here also.)

Page 15-16 - Working with Unipolar Stepper Motors.

Page 17, 18 - Working with Bipolar Stepper Motors.

Page 19 - Interfacing with Servo Motors. Note the Capcitor & Resistor.

Page 20 -  Working with Counter Modules.

Page 21-23 - Using 7-Segment LEDs.

Page 24 - How to control Solenoids.

Page 25 - Smart Wire

Page 26-27 - Switches, (Reset, Noise, Debounce-- noisy contacts.)

Page 28 - Working with POTS, (Potentiometers.)

Page 29 - Using LDRs, (Light Dependant Resistors.)

Page 30 - How to wire a Thermistor.

Page 31-42 - Working with LCD Displays.

Page 43-46 - Interfacing to a PC, (Computer), via Serial connection.

Page 44 - MAX232 Serial Interfacing.

-------------  For some reason, the following are missing in Manual #3 v4.4 -------------

Page 45 - Enhanced Serial Circuit. (see my schematic above for details).
                This is all that is needed to program a PICAXE.

Page 49 - Hard-Reset

Page 69 - Digital In, Digital Out, Analogue.

Page 76 - Making Sounds: Buzzer, Piezo, Speaker.

Page 77 - Switches.

Page 78 - LDR (Light Depandant Resistor).

Page 79 - DS18B20 Temperature reading device.  Use a pull-up
                4.7k resistor between the output of the DS18B20 and VDC.

Page 83 - Using Interrupts

Page 105 - FAQ's

NOTE:  Code is mixed within the circuit's...some quite generously.

NEW additions:
I2C is a 2-PIN connection between the PICAXE and the I2C device(s).
Both lines should have a 4.7K resistor from the SDA and SCL lines
and connected to VDC at the other end of the resistor's. Only need this
ONCE on each LEG, no matter how many I2C devices are connected. 
See page #6 of the AXE033.PDF manual.

1-Wire devices-- there should be a 4.7k resistor between DQ LEG and

Also see this link to FAQs here


Here is a breakdown on the LEG/PIN assignments of an 08M.
This will be true for any PICAXE, but will have other LEG/PIN
assignments. So a LEG is the physical Leg on the device; where as
the PIN has the assignment for what ever feature it can handle on
the LEG. Below is an explanation of how this is done with an 08M.

Ok, let's look at the facts-- we will use the 08M on the LEGs/PINs assignment.

1. Currently there are I/O lines that do not necessarily match the same physical LEG to the
    same use of that device. (i.e. On an 08M Physical LEG 3, is an IN/OUT PIN 4).

2. According to Manual #1, pg 27 08M-- Physical LEG2 is STRICTLY Serial IN
    It should also be hooked-up to the 22k & 10k according the the diagram on that page.
3. Physical LEG 4 is Strictly an IN PIN 3 (i.e. use a switch to trigger something.)

4. Physical LEG 7 serves two purposes. OUT 0 and SERIAL OUT (output ONLY)
    Serial OUT is sent back to the PC, and with the 'debug command', you can
    watch your Computer Monitor to see what is happening. This PIN also is used
    by the 'Program Editor' to let it know that the PICAXE programmed correctly.
   (Also note on pg #45 that 180Ω resistor is added. Good practice.)
    That's your first OUTPUT PIN 0

5. LEG 6 is   IN/OUT PIN 1    plus it can be used for ADC circuits.

6. LEG 5 is  IN/OUT PIN 2 

7. LEG 4 is   INPUT PIN 3   ONLY!

8. LEG 3 is IN/OUT PIN 4


So let's recap:  LEGS 7, 6, 5, 3 are OUTPUTS
                       LEGS 4, 6, 5, 3 are INPUTS

Notice that LEG 6, 5, 3 are the TRUE I/O PINS.

Bypass Caps are NOT an option ...put them IN even if running
on Batteries. .1uF is a good practice and it won't cost but pennies to do so!
Might as well take care of noise and one less thing to be concerned about.

One more item, when the Programming Cable is NOT
plugged in , take a 10k resistor from LEG 2   (Serial IN) to J1 then ground .) 
This has cleared up more then once, spurious problems hardware people have found.

Hope this helps out, fellow NEWBIE PIXsters!

Copyright © 2008-   Ted J. Mieske
All Rights Reserved.