We use cookies to provide our visitors with an optimal site experience. View our privacy notice and cookie notice to learn more about how we use cookies and how to manage your settings. By proceeding on our website you consent to the use of cookies.
Hello!
I am building a solar installation with a power requirement of 9 VDC. However, the only solar panel with rechargeable battery that I could find supplied 12 VDC (Tycon Systems RPPL12-18-15). To bring the voltage down to 9V, I used the LM317AT/NOPB wired in a circuit as such, with the following pinout:
When I tested the circuit outdoors at my office, it supplied 9V as expected. However, when I moved to the installation site, it started supplying either 0V (or close to 0), or between 6.7 and 6.9V. I had a spare LM317 and replaced it, but got the same result.
Low input voltage is the most likely cause, followed by a bad connection somewhere, high-frequency instability from some cause, or activation of a protection function.
Draw out or borrow the circuit from a datasheet, measure the voltage at each node relative to ground, and check how much current the load’s drawing. Whatever’s not as it’s supposed to be is a pointer to the problem.
The input voltage was measured to be around 13V. I checked continuity with a multimeter everywhere, with good results. Voltage across R1 was about 0.92V and across R2 was between 5 and 6V (not as expected). I was worried that the LM317 was protecting itself from overheating but it appeared to feel cooler than the outside temperature when I touched it.
I don’t currently have the appropriate probes to wire the multimeter in series in order to measure current. Do you have any other suggestions, or another solution to take the voltage from 12V to 9V without the LM317? Thanks so much!
