I have just done a comparison of voltage readings from three different power supplies on this circuit. Can anyone comment on my reasoning.
The third PS is a power plug for from the base unit for our home phone which is branded Panasonic and I am quessing is unregulated. While rated at 9VDC it measures at 14.3 with not connected. When connected to the 9V power plug, the lm317 regulating the 7V is only marginally warmer compared to when connected to my benchtop PS.
1- Benchtop PS, 12V ?A
2- Unregulated? power plug, 9V 800mA (from Panasonic remote phone base unit)
3- Regulated power plug, 12V 1A
* Measurements are VDC
- - Full Load / 5mm LEDs only / 1W LEDS only / No load
1- 7.6 / 11.9 / 7.7 / 12
2- 8.5 12.9 8.6 13.5
3- 11.7 / 11.9 / 11.7 / 12
Not knowing anything I would take the above to indicate that:
1) The regulated (12V) power plug will supply around 12V no matter what the load so I would have to heatsink for max the capacity of the powerplug,
2) that both my benchtop PS and the 9V unregulated power plug will supply relative to the load so the thermal buildup will not be as great and heatsink requirements less if not marginal, and
3) the regulated 12V power plug is unsuitable for this application with the circuit as is (capacitors being a separate issue).
My aplogies, tabs don't seem to work in adavnced text mode or the table would be easier to read and I may not be quite right in my terminology