A Defines Request

[cncmachineguy]

Kirk, I agree that Dave's suggestions are spot on. but also no arguing with actual blown up parts. If this were my project, I would start by disconnecting everything and reconnecting it 1 at a time. I would start with the LED's (and add resistors) then I would add the pot section, lastly I would add 1 coil circuit at a time.

I would suspect the answer can be found with the hardware, but sorry I do not know exactly what is wrong. Your pot circuit looks odd to me. I thought the path was Vcc->cap->pot->gnd. with the signal taken from between the cap and potthrough another resistor. Your diagram seems to show the pot parallel with the cap.

There is clearly some direct short somewhere through the guts of the PIC. maybe this has to do with the type of internal circuit for one of the pins. ie: open collector or totom pole.

As for blowing a 7805, I have never acheived that. they have alwys shut down before then. This is why I think a direct short has to be the problem. the current is spiking so fast, it can't turn itself off before destruction.

Keep this in mind also: even though the hardware worked on the stamp, as you know this will be running much faster, so maybe some back emf from the coil or possibly something else. just saying remember all things are not equal


code tags are this: add [code (other bracket), then your code, then bracket /code] and it will put your code in a nice scrollable box

[mackrackit]

I normally use a 470 ohm for the typical LED when the voltage is ~5 , not as bright as could be but safe. Bruce spells it out here.
http://www.picbasic.co.uk/forum/show...6966#post76966

Like Bert said, do one thing at a time. Trouble shooting can be a pain.

[Kirk Fraser]

I'd like to explore my theory first, considering my accomplished tests sufficient proof (so far) that the two global commands don't help in my circuit. What other commands are there to try? What commands would convert or leave the 3 essential pins analog and make the rest digital?

This seems reasonable since the PWM outputs are analog signals and driving the IRL530's with a solid digital on could act like a short, allowing coil current to build and eventually blow things up. This could explain the blown chips with the global commands.

The "normal" inaction with the POT input may also be affected by a more specific analog input, compare, or conversion command. The exact same POT circuit was used successfully with the Stamp, with the exact same RCTIME command. RC means Resistor-Capacitor so it is necessary for them to be in parallel to create a measureable oscillator time change when the POT value changes. I don't know why it is connected to ground instead of 5+ but I got that circuit from Stamp docs. Perhaps a different setting for that pin is needed to accept analog input from ground instead of positive values.

I don't know how the guts of the Analog - Compare commands work, if there's any need to know. I do think finding pin specific commands would be a step toward a solution. What section of the book are those in? Thanks.

[cncmachineguy]

Look up ADCON1 register in the datasheet. to find it faster, make sure bookmarks are on and scroll do the the A/D section. this section will tell you lots of stuff about how the pic does the A/D. the registers are always listed at the end of the section. BTW, within the first few paragraphs it explains how to turn the Analog input on and off to use the pin as Digital or analog. Any way, look up ADCON1 and read which bits need to be on or off, 0 or 1, set or clear.

PWM is not an analog output.

[Kirk Fraser]

Bert,

I'm pretty sure the reason it doesn't work is some kind of setup is needed for the A/D like there was when the LED test wasn't working. My explination of how the burnout works may be imperfect but it's gotta be close. Whatever the reason, if either output pin defaults to "1" when not setup, that would trigger the IRL530 to max out its coil.

I need to know something about how registers work - do they execute in sequence like a program? If I set ADCON1 =15 that turns off the A/D for all pins, then I set ADCON0 = 3 will it turn on A/D for Port.A0? Or will it ignore it if written in reverse order? Or can I assume the A/D defaults to off when not set up then perhaps only the ADCON0 = 3 would be necessary?

I don't quite understand what a comparator is. I understand the digital "or" but how does that handle A/D? I'd think CMCON = 7 should be ok unless required for A/D. Perhaps its safer (to conserve my remaining PIC chips) to assume the register is completely unnecessary in my application.

PWM is not strictly a digital signal since the width of each pulse can vary but it doesn't need conversion from digital to analog by the A/D converter, with the output bit set, does it? On page 151 item 15.4.4 is a list to set up PWM. Does PBP do any of that when the PWM command is used? I'm guessing not because of the burnt chips. So how do I tell which pins can receive a PWM output command? Do I use ordinary or enhanced PWM?

It would be nice if PBP did everything it could including setting up each chip function when called.

Kirk

[BobP]

Hi,

Only had time for a quick look. But from what I can see on your diagrams in post 1. The back EMF diodes are not correctly fitted and seem to be connected differently to the prototype board. The diodes should go across the coil contacts with the 'band' connected to the +ive coil side.

This seems reasonable since the PWM outputs are analog signals and driving the IRL530's with a solid digital on could act like a short, allowing coil current to build and eventually blow things up. This could explain the blown chips with the global commands.

The Pulse Width Modulator outputs are digital. The on and off time is variable and is what you adjust within the program. The amount of high back EMF that PWM will generate on this circuit will wreck havoc with the PIC. Move the diodes and test the circuit by replacing the coils with small lamps .

Also good pratice to fit 1k resistors to the gate connections from the PIC as directly connecting the PIC to the FETs can cause a 'lock on'.

Bob.

[Kirk Fraser]

Bob,

Thanks, I've added 1K gate resistors and replaced the coils with LED's for testing which should save some parts from burnout. The diodes are electrically connected according to your description, just not near the coils.

Back to learning how to set up the PWM command.

Kirk

[BobP]

Hi Kirk,

If you can use bulbs you will see the PWM better. Let us know how you get on?

Bob

[Kirk Fraser]

I put in the program revision below but again nothing happened. Since all my stuff is already posted earlier, I thought just discussing this section would be most efficient. Any discussion on content or how I can learn to improve the content is welcome. Thanks.

'*** Start of help request ***
DEFINE OSC 48
@ __CONFIG _CONFIG1L, _PLLDIV_1_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L
@ __CONFIG _CONFIG1H, _FOSC_HSPLL_HS_1H
@ __CONFIG _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H
@ __CONFIG _CONFIG2L, _PWRT_ON_2L & _VREGEN_ON_2L
@ __CONFIG _CONFIG3H, _PBADEN_OFF_3H & _MCLRE_OFF_3H
@ __CONFIG _CONFIG4L, _LVP_OFF_4L & _XINST_OFF_4L
ADCON0 = 3 ' Setup PortA.0 for A/D function
OSCCON = %01110000
'*** End of help request ***