paul george
Member
Will a picaxe 28X2 work on picaxe 28 starter board??
picaxe 28
- Thread starter paul george
- Start date
Provided the pull-downs on the C.0-C.7 port are not a problem, then yes. But, depending on what you want to do, there might be an easier way, as the 28X board has no download circuit and uses ribbon cables to connect, which may not be very convenient. An alternative might be to wire your own board using a standard dil-specific protoboard such as the radioshack 276-168B or similar.
paul george
Member
I want to connect 8 servos to the starter board..should I modify the board in any way??
paul george
Member
Wanted to make small humanoid..
Do you suggest a arduino or picaxe for such a project??
Do you suggest a arduino or picaxe for such a project??
grim_reaper
Senior Member
PICAXE, obviously. But then, this is a PICAXE forum!
westaust55
Moderator
The AXE020 starter board does have a download circuit. Also has a ULN2803 and space for an L293D H-bridge motor driver chip.
There is also a pull down resistor array for the PortC pins.
An alternative board might be the AXE022. This board has the program download circuit and no other chips or pull-down resistors so it could be more flexible particularly if you only wish to control servo's. There is provision for an onboard EEPROM if you wish/need to hold a lot of data onboard or maybe even an alternate program.
The PICAXE chips can each control up to 8 servo's via PortB IO pins.
There is also a pull down resistor array for the PortC pins.
An alternative board might be the AXE022. This board has the program download circuit and no other chips or pull-down resistors so it could be more flexible particularly if you only wish to control servo's. There is provision for an onboard EEPROM if you wish/need to hold a lot of data onboard or maybe even an alternate program.
The PICAXE chips can each control up to 8 servo's via PortB IO pins.
BeanieBots
Moderator
The AXE020 is the board I find most useful for quick and easy servo projects.
Simply remove the ULN2803 darlington driver and replace it with a DIL resistor pack of about 330R.
If you also fit the full 3-way connector strips to the 'B' port outputs, servos with Futaba style connectors simply plug on directly.
Simply remove the ULN2803 darlington driver and replace it with a DIL resistor pack of about 330R.
If you also fit the full 3-way connector strips to the 'B' port outputs, servos with Futaba style connectors simply plug on directly.
paul george
Member
do you think weather a PICAXE 40X2 will be better for such humanoid, i hav already made a robot.
But am not getting any schematics for picaxe 40X2 circuit connection.
But am not getting any schematics for picaxe 40X2 circuit connection.
That depends on the complexity of your project.
Your question is unclear. Are you in need of the PICAXE Pinouts and Download Circuit?
"The AXE020 starter board does have a download circuit." So it does, apologies, I missed it when I had a look. The main point still stands however. The problem with ribbon cables is terminating them, which needs a pcb (bought or made) as the 0.1 pitch won't work with stripboard (unless you can cut between the holes), though if you can plug in the servos directly that works. But there is minimal expansion capability and a lot of stuff that perhaps isn't needed.
The difference between the chips is principally one of pin out, so the choice depends on your hardware requirements. As for being a humanoid, the real issue is how sophisticated your software is going to be and what input sensors it has to process. I suspect that you could make a nice demonstration robot with a picaxe, but depending on your ambition you might be getting into very advanced territory that would need multiple communicating chips and a lot of processing. If that is not your aim then a Picaxe should do nicely for starters.
The difference between the chips is principally one of pin out, so the choice depends on your hardware requirements. As for being a humanoid, the real issue is how sophisticated your software is going to be and what input sensors it has to process. I suspect that you could make a nice demonstration robot with a picaxe, but depending on your ambition you might be getting into very advanced territory that would need multiple communicating chips and a lot of processing. If that is not your aim then a Picaxe should do nicely for starters.
westaust55
Moderator
The 40X2 and 28X2 PICAXE chips both have the same set of commands, same memory. The primary difference is that the 40 pin chips have an addiitonal 11 IO pins (as a complete Port D and some extra PortA pins).
If you think that your project may ultimately need more IO you have two options:
1. the larger chip
2. multiple smaller chips.
Multiple smaller chips could enable separate programs for sub assemblies eg one for arms and one for legs but there will then be a need to to communicate between the multiple PICAXE chips.
paul george
Member
I want to know about the 40X2 download circuit..
paul george
Member
@geoff so what do you suggest other than a picaxe?
westaust55
Moderator
All of the PICAXE chips from 8 pin to 40 pin variants use the same download circuit.
The download circuit is shown in PICAXE manual 1 - See pages 43 to 45 here: http://www.picaxe.com/docs/picaxe_manual1.pdf
The download circuit in its most basic and typical form comprises two resistors and a 3-wire socket (a stereo socket of 3-pin header for example).
Optionally you can add a low value resistor (often 180 Ohms recommended in the PICAXE SEROUT line as well).
The two resistors are not used as a voltage divider but each has a specific function.
The 10 kOhm resistor acts as a pull down for the SERIN pin on the PICAXE chip. Whenever the SERIN pin goes high (can float high if no pull-down resistor fitted) the PICAXE firmware takes this to indicate a program is to be downloaded from a PC into the PICAXE chip.
The 22 kOhm resistor is a current limiting device. It accommodates cases where the user is programming from a PC serial port (9-pin type) where the output voltages may be higher than the PICAXE supply voltage. By the RS232 specification the voltage on the data pins for a PC serial port could be as high as +/-25 Volts. The resistor limits the current and in conjunction with the internal ESD diodes the voltage so that the PIC chips is not damaged when higher voltages are present.
The download circuit for the 40X2 is the same as the download circuit for the other PICAXEs.
There is a diagram in Manual1, see the section 'At a Glance - Download Cirsuit"