I'm thinking of cutting the trace to the LED, since I'm not a fan of dealing with unsoldering/soldering. https://forum.arduino.cc/index.php?topic=418850.0
Based on the post above, I'm still unsure which lead he cuts without ruining the Pro Mini.
Is it the lead to the resistor?
They recommend the MCP1703 LDO.
Low 2.0 µA quiescent current (typical)
Wide input operating voltage range: 2.7V to 16.0V
250 mA for output voltages ≥ 2.5V
200 mA for output voltages < 2.5V
Output voltage range 1.2V to 5.5V in 0.1V increments (50 mV increments available upon request)
Stable with 1.0 µF to 22 µF ceramic, tantalum, or aluminum output capacitors
I found this part on digikey and it has a 250 mA max. output current:
I was wondering is this considered an LDO as well?
It appears to be a better option quiescent current and output current wise. Plus the cost is not too different either. I can't find any mention of whether or not it's an LDO (Low drop out voltage regulator).
Is it's efficiency relatively the same?
Output voltage: 2.5 V to 6.0 V, selectable in 0.1 V step
Input voltage: 16 V max.
Output voltage accuracy: 2.0%
Current consumption: During operation: 30 uA typ., 40 uA max.
Quiescent current /During power-off: 1 uA max.
I think you should reconsider about desoldering versus cutting traces. For the power LED, you can desolder the resistor that feeds the LED. You just put your iron tip on the resistor body, and after a few seconds it will heat up the entire part to the point that the solder at each end melts, and you can just flick it away. The same works for me for the voltage regulator, although you have to wait a bit longer.
With respect to the regulator, there is also an MCP1702 which is about the same as the MCP1703 except that the maximum input voltage is a bit less. Then the MCP1700 only allows input up to 6V, but has a much lower dropout voltage than the other two - 178mV versus 625mV. If you are battery powered, the MCP1700 would give you longer battery life.
The other one you found on Digikey appears to require an external transistor to be added to the circuit. I don't think you want that.
But for really low power, you can order a 3.3V 8MHz Pro Mini, remove the LED resistor and the regulator, and power the Mini directly from the battery - an 18650 or some AAs. There would be no regulator at all. The Atmega328P will work fine, but any other parts on your circuit would need to work at varying supply voltages, and not require exactly 3.3V or 5V.
But you should know that Pro Minis with bad processors have appeared, and in deep sleep they draw several hundred microamps instead of less than one microamp. I don't know what the solution to this is. The last two batches of Pro Minis I got on Ebay were all bad. Here's a video on this problem:
The MCP170X regulators are indeed a good choice for ATmega328P projects.
The MIC5205 type (used an a lot of Pro Minis) and MCP170x use different pinouts of course, so you cannot simply replace the regulator on a Pro Mini with an MCP170x.
After reading the article I posted initially and the results the person got,
I'll desolder the resistor.
With respect to the regulator, there is also an MCP1702 which is about the same as the MCP1703 except that the maximum input voltage is a bit less. Then the MCP1700 only allows input up to 6V, but has a much lower dropout voltage than the other two - 178mV versus 625mV. If you are battery powered, the MCP1700 would give you longer battery life.
This will be great actually for either a battery setup or solar panels when the light decides to fade out throughout the day whether it's near sunrise or sunset.
I've been confused by dropout voltage after googling definitions several times.
I think I get it now.
It's the difference that must be maintained in input and output voltage before the device stops regulating the voltage.
Correct?
So what happens after limit has been reached?
The output voltage will be the same as the input voltage?
Or the device will just stop working and voltage/power is not is transferred to the rest of the circuit?
Regarding this how can you tell whether or not you need a transistor?
knightridar:
This will be great actually for either a battery setup or solar panels when the light decides to fade out throughout the day whether it's near sunrise or sunset.
I've been confused by dropout voltage after googling definitions several times.
I think I get it now.
It's the difference that must be maintained in input and output voltage before the device stops regulating the voltage.
Correct?
So what happens after limit has been reached?
The output voltage will be the same as the input voltage?
Or the device will just stop working and voltage/power is not is transferred to the rest of the circuit?
Yes, there has to be some headroom in order to do any regulation. What happens below the dropout voltage depends on the design of the regulator. It may pass through the input voltage, or it may shut down. In any case, there won't be any regulation.
Most regulators have the transistor built in. The S-816 is very much the exception. But I don't think 100mA is enough for general use. By the way, you haven't said what kind of project this is. Anyway, if you're going to go to the trouble of replacing the regulator on a Pro Mini, you might as well use one that will do 250-300mA, with very low dropout. But note srnet's warning that you have to use one that matches the pinout of what you're replacing unless you'll be making the regulator external to the Mini.
Most regulators have the transistor built in. The S-816 is very much the exception. But I don't think 100mA is enough for general use. By the way, you haven't said what kind of project this is. Anyway, if you're going to go to the trouble of replacing the regulator on a Pro Mini, you might as well use one that will do 250-300mA, with very low dropout. But note srnet's warning that you have to use one that matches the pinout of what you're replacing unless you'll be making the regulator external to the Mini.
I wanted to try modifying them, but again it requires time and not messing things up in the process. I've really been looking at just buying a low power pro mini or some of the newer versions of Arduino, but a lot of the custom low power boards from rocketscream, moteino, etc are relatively expensive for what they are IMO but I understand these are small developers and they have to make a return for their work to grow.
Although I wanted to focus on a custom board with efficiency and low BOM cost and 32 bit MCU, and speed in mind and make it open source just like Arduino.
I'm working on multiple projects that these can be potentially used on. I'm thinking of just going to the gigs section and having someone design a board for me.
Some projects will deep sleep and wake up from time to time, some will be on all the time.
Some of the projects that I want to use these for:
solar powered solar tracker with no batteries
solar powered indoor soap dispenser
solar powered indoor/outdoor atomic clock + solar powered weather monitor + gps module
Potential solar panel for indoor and out door use.
I found this neat example for indoor power, but again BOM cost gets higher.
It has I believe MPPT, voltage booster, super capacitor and a bunch of other features:
Current Limit (Adj. or Fixed)
Open Circuit Protection
Over Charge Protection
Over Discharge Protection
Power Good Output
Shutdown, Enable, Standby
Some genius from analog devices came up with the reference design and I saw them showing it at a trade show on Youtube:
Kevin Darrah sells a 328P "breakout" board for $10 in his Tindie store. It's basically just the processor, crystal, resistors and capacitors, and the headers. But no regulator or LEDs. You can see them in this video:
Kevin Darrah sells a 328P "breakout" board for $10 in his Tindie store. It's basically just the processor, crystal, resistors and capacitors, and the headers. But no regulator or LEDs. You can see them in this video:
