30w low voltage PWM controller

[SillyOldDufferModerator @sillyoldduffer]

PICAXE is still going.   Has all the virtues and vices of an educational system:

• for simple applications rather than complex
• limited number of boards and add-on modules
• quite expensive – the starter kit is about £50. Might be just what’s needed, or not.  Decide yourself!
• interpreted, not compiled, so will on the slow side
• only works with pic chips pre-loaded with the PICAXE interpreter
• requires a special cable
• programmed in a language that’s vaguely like BASIC.

Example:

for b1 = 0 to 63 ; start a loop
sertxd(“The value of b1 is ”,#b1,13,10)
pause 1000
next b1 ; next loop

Though the PIC chips and language are potent PICAXE is closed source.  That severely limits community support, so the number of add-ons is pitiful compared with Arduino and others.   The number of microcontrollers supported is small too – a subset of the PIC family, whereas the Arduino-IDE supports many different hobby and professional development microcontrollers – not just Arduino.  Here’s what the PICaxe forum says about Arduino vs PICAXE support .

Chief selling point is the claim that PICAXE is simple:  certainly true in a classroom, but after that, I doubt it.   I suspect Bazyle is right about BBCMicroBit – it too is aimed at education, with an even simpler drag and drop load mechanism.    The raspberry Pico with Python is also drag and drop, well worth considering if you want a cheap powerful board and a modern language.  If Python performance isn’t good enough, or doesn’t support a module, Picos can be programmed in C/C++.   It’s not boxed in like PICAXE.

Dave

 

 

[Robert Atkinson 2Participant @robertatkinson2]

The RaspberryPi Pico series are impressive but a bit overkill as a 555 replacement 🙂

[duncan webster 1Participant @duncanwebster1]

555 has the great advantage of a much larger output current, 200mA if I recall correctly. It can be used for all sorts of things apart from timers, latching flip flop comes to mind

[Robert Atkinson 2Participant @robertatkinson2]

PicBasicPro directly supports both software (any device any pin) and hardware (needs a pic with one or more PWM modules) PWM.The hardaware commend is:

HPWM Channel, Dutycycle, Frequency

The frequency is only limited by th clock frequency the PIC is clocked at.

[duncan webster 1]

On duncan webster 1 Said:

555 has the great advantage of a much larger output current, 200mA if I recall correctly. It can be used for all sorts of things apart from timers, latching flip flop comes to mind

I should perhaps have mentioned … There is also a BB variant of that little 1803 module, with higher current rating, and a heatsink.

MichaelG.

[John HaineParticipant @johnhaine32865]

Having cracked the chip programming problem I’m now wondering about using a pic in another project where it would be useful to write c code. Any suggestions for suitable tools other than the Microchip mplab bloatware please?

[Robert Atkinson 2Participant @robertatkinson2]

MicrocodeStudio is included with PicBasicPro3 even the free Student version. Note you don’t have to be a student any personal, non commercial use is OK. They also sell programmers and development boards.

http://www.pbp3.com

https://melabs.com/

Robert.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

The RaspberryPi Pico series are impressive but a bit overkill as a 555 replacement 🙂

If overkill is decided by counting transistors then all microcontrollers are out, including the PICs Robert recommended earlier!

But utility, cost and convenience are far more important than transistor count.  The extra functionality provided by a microcontroller becomes attractive when it costs the same as an NE555, or cheaper. And dominates if the electronics have a complex function.

The PWM board identified by Michael is as simple as it gets, so the NE555 is a good solution.  But the NE555 struggles beyond that -doing more requires extra electronics, adding cost and complexity.   Simple is good, too simple is bad.

Most microcontrollers have internal hardware that outputs fast, phase correct, and phase & frequency correct PWM on several pins.  And programmers can write code to ‘bit bang’ PWM as well.  Much easier to build a multi-motor system with a microcontroller than NE555s.

Modern electronics designs use microcontrollers galore;  billions of them sold worldwide.  Cheaper because they keep component counts down and improve flexibility – features can be added and changed by reprogramming rather than altering the hardware.

The Pico is interesting because its microcontroller contains two fast Cortex CPUs, with 8 PWM outputs each.  If 16 PWM outputs aren’t  enough, there are also 8 independent state machines that can be programmed to do PWM – at high speed.

I have huge respect for the NE555 – it’s brilliant.  But time marches on, it’s not 1975!  Fifty years later, microcontrollers are even more brilliant.  As always the problem is keeping up.  Using the NE555 is relatively simple electronics.   Microcontrollers require entirely different skills, not easily acquired!

Dave

 

 

 

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

MicrocodeStudio is included with PicBasicPro3 even the free Student version. Note you don’t have to be a student any personal, non commercial use is OK. They also sell programmers and development boards.

http://www.pbp3.com

https://melabs.com/

Robert.

John wants to write ‘C’, not BASIC.   Is that supported?

Dave

[duncan webster 1Participant @duncanwebster1]

When I played with PICs 20 plus years ago to read a pin you had to put some mantra like

If(PORTA & 0b00100000 == 0b0010000)

etc

Which isnt as easy as Arduino digitalRead.

And there was a lot of rhubarb at the beginning about brownout and similar, which again you don’t get with Arduino. Has it improved? If so I might be tempted.

 

[SillyOldDuffer]

On SillyOldDuffer Said:

On Robert Atkinson 2 Said:

MicrocodeStudio is included with PicBasicPro3 even the free Student version. Note you don’t have to be a student any personal, non commercial use is OK. They also sell programmers and development boards.

http://www.pbp3.com

https://melabs.com/

Robert.

John wants to write ‘C’, not BASIC.   Is that supported?

Dave

Doh! missed that. Not being a C person I can’t help much but the compliler you are using is a good starting point for a search.

Robert.

[duncan webster 1]

On duncan webster 1 Said:

When I played with PICs 20 plus years ago to read a pin you had to put some mantra like

If(PORTA & 0b00100000 == 0b0010000)

etc

Which isnt as easy as Arduino digitalRead.

And there was a lot of rhubarb at the beginning about brownout and similar, which again you don’t get with Arduino. Has it improved? If so I might be tempted.

 

Yes it has improved a lot.
PBP3 can be as simple as PortA.1 = 1 (or 0 or a variable name). It automatically sets the pin as an output and high. You acn also make an alias e.g  RedLED VAR PortA.1 Then RedLED = 1 (or 0) will turn a LED connected to PortA.1 on or off. Much easier to keep track of in code.
To read a port just say x = PortA.2 etc.
You can still set and read the registers directly of you  want to….

Robert.

 

[SillyOldDufferModerator @sillyoldduffer]

I’ve bruised my brain trying to remember what complier I used for my circa 1990 PIC capacitance meter.  Unlike my brain the meter still works.  Good job I didn’t bet the farm on it being bog standard gcc.  Whilst it can cross-compile for a long list of processors, doesn’t do PIC!   My guess is I used whatever Microchip compiler had at the time, quite likely a customised gcc.

The latest versions might do what John wants:  the XC16 installer is 118Mb on linux, and might expand considerably.  It’s a customised gcc.  Note there are 4 compilers, which one is needed depends on the target PIC.

I’d go with MPLAB : though big, it has everything needed.

Dave

 

 

 

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

On duncan webster 1 Said:

When I played with PICs 20 plus years ago to read a pin you had to put some mantra like

If(PORTA & 0b00100000 == 0b0010000)

etc

…

…
PBP3 can be as simple as PortA.1 = 1 (or 0 or a variable name). It automatically sets the pin as an output and high. You acn also make an alias e.g  RedLED VAR PortA.1 Then RedLED = 1 (or 0) will turn a LED connected to PortA.1 on or off. Much easier to keep track of in code.
To read a port just say x = PortA.2 etc.
You can still set and read the registers directly of you  want to….

Robert.

 

Just for fun, it’s not difficult to extend C++ so Arduino supports similar syntax.

After declarations like LED = pin(13, OUTPUT)  P12 = pin(12, INPUT);

then

LED = HIGH;  // set the LED pin HIGH
int i = P12;      // read pin12 and copy the result to i.

My implementation below is only syntactic sugar in that it simply wraps digitalWrite() and digitalRead().  But I could do the reads and writes  with Duncan’s much faster register bit twiddling.

The last two lines overload the = operator, changing it’s built-in copy behaviour to either read from or write to a pin. Unlikely that a BASIC compiler supports operator overloading.

Whilst there’s little point in operator overloading in an NE555 replacement project, the capability (and other advanced compiler features) become extremely helpful in larger projects.  Like writing a BASIC compiler so busy people can program a PIC to do PWM without needing a degree in Computer Science…

Dave

 

 

 

[Robert Atkinson 2Participant @robertatkinson2]

The whole point of PBP 3 is that you don’t have to to do anything complex for simple projects. For PWM with a pot it’a as simple as:

PWMloop:

setpoint VAR byte

ADCIN 1, setpoint

HPWM 1, setpoint, 1000

GOTO PWMloop

This reads a potentiometer on ADC input 1 to variable setpoint and outputs a corresponding PWM output at 1kHz on PWM output 1.

Robert.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

The whole point of PBP 3 is that you don’t have to to do anything complex for simple projects. For PWM with a pot it’a as simple as:

PWMloop:

setpoint VAR byte

ADCIN 1, setpoint

HPWM 1, setpoint, 1000

GOTO PWMloop

This reads a potentiometer on ADC input 1 to variable setpoint and outputs a corresponding PWM output at 1kHz on PWM output 1.

Robert.

I understand that a simple language is good enough for simple projects, but that’s not the point. The issue is that a simple language isn’t good enough for complex projects!

Engineers should always be aware of limitations.   What happens when a project comes along that’s too big for BASIC and/or can’t be accommodated on a PIC?

The answer is to use a language like C that provides more tuning features, and/or to switch to a more powerful chip. C, being mostly standard, simplifies porting projects to different chips.  PBP3 BASIC is PIC only, a dead-end.

Being told BASIC is easy doesn’t mean it actually is, or that C/C++ is necessarily more complicated.  Here’s the Potentiometer controlled PWM C code for Arduino.   I suggest it isn’t more difficult than Robert’s BASIC example, and some might think it’s simpler.

Starting out with microcontrollers, I’d recommend Arduino over PIC and BASIC.  Apart from the glass ceiling being much higher, Arduino comes with a huge library of interfaces to a multitude of sensors and peripherals.  Someone else has done the hard-work.  And being based on C/C++ makes it relatively straightforward to switch to mbed or an RTOS, if that’s required.

Being involved in a few failed professional projects made me sensitive to the horrible consequence of choosing technology that runs out of steam and can’t deliver.  In 3 cases, the boss chose simple and quick tools, only to find they couldn’t meet the full user requirement.    If I may draw an analogy, Enid Blyton’s Noddy books require a reading age up to 5 years.  All good provided one sticks to “Noddy and the Bumpy-dog”, but that level of English isn’t good enough to decode an adult novel or a legal document.   Same issue with tools generally: you can’t turn railway wagon axles on a Sherline!   And though my Vauxhall Corsa is good for light load local commuting, it struggles with heavy loads and long distances.  That an individual happens to manage with a reading age of 5, a Sherline, and a Corsa does not mean that these tools are good enough for everyone and everything.  They aren’t!!!

Dave

[Robert Atkinson 2Participant @robertatkinson2]

The point is we are not talking about complex projects. I’d argue that an ardunio and it’s IDE is not really a microcontroller it’s a microcomputer. The DUE for example has a 32 bit ARM Cortex processor. IT uses a C++ based Object Orientated languge. Great if you want to learn programming and move on to advanced progects with wed interfaces colour displays etc etc. Ifyou just want to acheive a simple task then PBP3 has a lot lower learning curve especially if you used home computers in the 80’s and 90’s as a suspect many of us did.

I find the Ardunio an similar libaries a mixed blessing. Thet make things easy but don’t help understanding of fundamentals and can lead to bloated software.

Robert.

[John HaineParticipant @johnhaine32865]

 

Dave

Or even…

analogWrite(ledPin, 0.25*analogRead(analogPin);

I’ve got a job coming up where in response to a pulse every second I have to output 13, 13, 14, 13, 13, 14…. pulses.  Easy (probably) on a PIC and it only needs one input and one output pin so an 8DIP package would do fine.  But I’ll actually use a Pico or (maybe) a Nano, because I have spares, I know how to program them (actually I have code which does it), I’ve got the tools, and they can do other functions.

No prizes for guessing what it’s for.

But this has been a very useful thread and now I know how to turn PIC 12f675s into precision timers!

[IanTParticipant @iant]

Not ‘C’ I’m afraid but on a Picomite (in very simple terms) it could look something like this.

I’m sure there are other/better language solutions – but this is the one that works best for me.

Regards,

 

IanT

 

 

 

[duncan webster 1Participant @duncanwebster1]

RA2’s post has convinced me to have nothing to do with Basic, the Arduino code is so much easier to understand, and I used to do Basic on a beeb many moons ago

[Robert Atkinson 2Participant @robertatkinson2]

Hi Duncan. Not quite comparing apples with apples. SOD’s code is commented and a screen grab from a colour coded development environment. Mine is just the uncommented code. SOD’s code does not seem to set the PWM frequency.
Do you really understand the purpose of the void setup() and void loop() constructs in SOD’s code?

My earlier code has a mistake with the variable definition inside the loop Corrected with comments

setpoint VAR byte              ‘Define a setpoint as a 8 bit variable

PWMloop:                         ‘Label for start of loop

ADCIN 1, setpoint             ‘Read voltage on ADC 1 input to setpoint

HPWM 1, setpoint, 1000    ‘Write setpoint value to hardware PWM output 1 with frequency of 1kHz

GOTO PWMloop                ‘Loop back to start.

Is that any easier?  It runs on a 8 bit 4MHz 1kB pic with no libaries, operating system or interperter. Not a 133MHz dual core ARM Cortex, 257kB of Ram and 2MB of Flash. Yes the Pico is cheap but it’s overkill. It also consumes 50mA compared to 0.5mA for a PIC.

Robert.

 

[duncan webster 1Participant @duncanwebster1]

Ive been writing C for years, Arduino is a dialect of C. I suppose its what you’re used to, but you can exploit the full power of C if you want to. And yes, I think I understand setup and loop. I never mentioned pico, I tend to use nano or pro mini. If I feel the need to use PIC I’ll still want to use C, why learn something new if it’s less powerful.

[Robert Atkinson 2Participant @robertatkinson2]

OK, You didn’t say you were competent with C. IT a bit unfair to say PBP code is hard to understand when you already know C. It’s a bit like saying German is easier to understand than French when you already know German.
Obviously there is no point in learning PIC Basic Pro if you know C. I’m only recommending it for beginners to programming who want to do simple projects.
There is a free C complier as part of the MPLAB IDE if you feel the need to do some “naked” chip work.

Robert.

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