I have a set up that seems to run in a stable way ‘most’ of the time.
Every so often the set up fails. I have finally seen that the 5V voltage regulator has been damaged. See pic.
The little pimple on the reg (circled) suggests to me that it has overheated.
The unit runs from a 12 Volt battery 9.6 Ah that is being charged from a solar panel with a 12 Volt 6A Charging regulator.
What would cause this to happen on an irregular basis. I have a few units that have never had an issue, and others that have died, and I assume that this is the cause, although it is the first time I have actually been able to ID the issue.
Any thoughts or guidance would be appreciated.
That certainly is a bit odd. What battery type are you using?
The absolute maximum voltage an AMS1117 can handle is a paltry 15V. It’s entirely possible that close to that is coming through from your solar regulator - not constantly but perhaps the peaks are close to that.
Other thoughts to consider:
- How much current is being drawn through that regulator? Is it simply being overloaded?
- Do you often disconnect the arduino from the supply battery?
Below is a typical application from the datasheet.
D1 is an often overlooked component - it protects the regulator against Cout discharging backwards through the reg when Vin falls low. I can see you have a diode on-board (labelled B2) but I can’t tell if it’s a reverse-polarity protection or if it’s fulfilling the purpose of D1.
Thanks for the comments.
The battery is a sealed lead acid battery.
I should point out that I am more of a biology person than an electronics one so if I ask a dumb question, this is why.
The peak is a possibility I guess. The place I have had the most trouble is up north Queensland, so I guess they could get more solar ‘grunt’ than Victoria.
I do not believe I am overloading the Nano too much.
Would another voltage regulator up stream of the Vin pin make sense? Use one at 7V or similar? If so, any amp recommendations?
Thanks for the help.
Pre-regulating might be a good way to proceed. Here’s a roughie
The LM78xx series of regulators have a more robust input. A 9V reg (7809) will do nicely. If you already have a 7V that will be fine too.
That is great, thanks for the schematic, that really helps.
A couple of additional question if I can? To further my understanding of capacitors.
You have a 1 uF and a 100 nF cap on the downstream side. My questions are:
Is there a reason that you use a 100 nF and a 1 uF cap instead of say a 1.2 uF cap. (Noting I don’t know if 1.2 uF exist) I just want to understand if the different values perform different tasks. Or was there a need to simply get slightly more than 1 uF of capacitance in that side of the circuit.
I assume that the exact positioning of the diode between the two caps is not necessary, it is just how you drew it. Correct?
Correct. Because this is a “schematic” we’re really only interested in the electrical connections. The physical layout of a circuit (how much wire goes where or if the capacitor goes closer to A or B) isn’t super important at the hobby level - though it is a consideration when working with signals or higher currents.
Short answer: The exact values of the caps are not important - small caps have certain desirable properties, and larger caps have other certain desirable properties. A 22nF and 10µF would perform about the same job roles, just subtly (and unimportantly) differently.
While capacitances do sum together (in this case to 1.1µF) that’s not the purpose.
100nF are often used as a bypass capacitor: any “high” frequency signal (supply transients) pass through the 100nF capacitors to ground. It’s like having a selective short-circuit, that only shorts out rapidly changing voltages - it leaves the actual DC alone.
As for the 1µF cap: Here the capacitance is 10x greater than 100nF, so it is less suited for bypassing high frequency signals and more suited for acting as one usually thinks a capacitor acts - it’s just a reservoir. A belt-and-braces addition that many people make. You’ll often see one on the input side too.
None of these caps are strictly necessary. In my opinion the most important is the 100n on the input since it helps protect the input stage. The other two you could easily live without, since there’s still two more regulators downstream and the nano has onboard regulation/caps anyhow.
Great explanation. Much appreciated. As a learner in life I like to understand the why of things. So this was really helpful.