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Finding the Minimum frequency value that the PIC can generat
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MCUprogrammer



Joined: 08 Sep 2020
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PostPosted: Fri Mar 17, 2023 3:38 am     Reply with quote

The link is as follows
I energize the test board with a 12V adapter. I'm connecting the serial avometer to the 5V output output of the 7805. On my board, led, lcd and button are connected. I'm looking at the current it draws during operation. What interests me is the current it draws during operation.
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Ttelmah



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PostPosted: Fri Mar 17, 2023 7:10 am     Reply with quote

The button should draw nothing unless pushed.
The LED will draw current. Depends on the dropper resistance and the
type of LED.
The LCD is probably the biggest consumer. Is it text, or graphic, does
it have a backlight?.
However you also don't mention the PWM. If this is driving something,
this will draw power.

The way to reduce power is to think about _everything_.

The actual PIC will be the smallest part of your consumption.
The key in power is to turn things off when they are not used.
Set lines to the direction that draws the least power.
temtronic



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PostPosted: Fri Mar 17, 2023 8:23 am     Reply with quote

yes, LCD back lighting will draw a LOT of power as they use LEDs. The actual LCD electronics doesn't take a lot of current. I've run 5V LCD modules from 3V PIC I/O pins in a previous project.
pullup/pulldown resistors can draw power. while a 10k pullup doesn't consume much,a 1Mr consumes far less.....
MCUprogrammer



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PostPosted: Fri Mar 17, 2023 8:35 am     Reply with quote

I understand. I'll deal with the flow thing again later. What method should I apply for current PWM? To do with the dsPIC33EV series
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temtronic



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PostPosted: Fri Mar 17, 2023 9:52 am     Reply with quote

If you mean 'how much current does the PWM' use. You can look on the datasheet to see what power is saved when the PWM module is disabled but...
the general rule of CMOS is that it's the number of transitions (high-low) that determines current (power) used. Same as the PIC 'clock' rate, go slow means very little power used, go fast, lots of power used.
It also depends upon the 'load' resistor or device attached to the PWM pins.

hmm, you started off with an 18 series PIC, now a dsPIC33 series and since this is NOT a battery powered project, actual current/ power used is not a big issue. I've not used dsPIC series but I suspect there's a LOT of necessary reading involved in the 100s of pages in the datasheet in order to maximize power savings.
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