Preliminary warning on cheapo wallwarts
Unregulated DC wallwarts (the most common kind) are rarely labelled in a meaningful way. When a manufacturer sticks a "12V" label on a product it could mean:
- The voltage output by the wallwart when sourcing X mA will never fall under 12V. Under a lesser current load, the actual voltage is higher.
- The wall-wart will always deliver at least 12V, though some units in the batch might deliver 13V or 14V.
- 12V is the mean value, there's a 10% or 20% standard deviation around that.
As a result, be extremely cautious when using a power supply approaching the maximum ratings!
Regulated or switching mode PSUs are more trustworthy!
- 7.5V to 12V. The higher the voltage, the higher the heat on the 7805 and 7905 regulators. An input voltage above 15V, even for a short amount of time, is going to damage the LT1054 - as a result, there is a risk of damaging the Shruthi-1 even with a 12V supply (see the warning above).
- >200mA. Note that this is often wrongly reported on the power supply specs, so 300mA is a minimum.
- Switching mode PSUs have been known to work.
- Center tip positive.
- Farnell 1961443 (EU) ; 2060981 (UK)
- Hobbytronics (UK)
- Rapid: http://www.rapidonline.com/Electrical-Power/AC-DC-Unreg-Ptop-Psu-9v-DC-600ma-85-3911 (UK)
- Reichelt MW 3N06GS
- 1Spot Combo Pack from Sweetwater . (USA) This is great for multiple Shruthi's / MIDIpals. NOTE: it only comes with 2 Polarity Reversal Adapters, which you will need to power a Shruthi/MIDIpal. They can be purchased seperately or, if the PS is only being used for Shruthi's/MIDIpal's, the Adapter can be added at the PS Connector, just before the Multi-Plug Cable, causing all plugs then to be the proper polarity.
- Adafruit, Sparkfun and CoolComponents have a 1W, 9V switched mode PSU.
- 9V Battery clips can also be used. Adafruit ; Sparkfun
- 9V AC. 12V AC will cause excessive heating on the 7805 and is not recommended.
- Polarity does not matter.
- 5V to 9V. The higher the voltage, the higher the heat on the LM1117 regulator. Note that this is a LDO regulator, it should work with as low as 4V indeed!
- The MIDIpal draws less than 100mA, so current ratings should not be an issue.
- Center tip positive
- POWERPAX SW4305 ; Farnell SKU 1971788. This one is switched mode, hence very light and small.
- If you have a spare mobile phone charger (who doesn't?), it's probably worth checking the voltage it provides. Lots of them deliver 5v under a few hundreds mA. Generally, you can easily swap the plug with a standard Jack DC 2.1mm (beware the polarity!). A convenient and environment-friendly way of getting a PSU for little to no money!