According to IVP on Thu, 01/24/13 at 16:35: > =20 > "nominal" is used to categorise the cell. For example a NiCd > is nominally 1.2V (1.4V when freshly charged), a lead-acid > battery is nominally 12V (13.8V when freshly charged) etc >=20 > In the freshly-charged state, naturally they have their greatest > capacity. As Wikipedia notes, the discharge curve depends on > the current drawn. For circuits that draw very small currents > from alkalines the limit is the chemical shelf-life (10+ years) >=20 > I think in your situation you really need to measure both the > working voltage and current draw from a set of new batteries >=20 > If you want to be a complete anorak and get very involved - >=20 > A DMM will give you most of the story but a scope will tell > you if there are any significant pulse current draws. If you > don't see any, you can add resistance to the B+ line until the > tapestry starts failing and look for pulses then. You'll have > some idea of the pulse current by the voltage drop across > the resistor. It might not be terribly accurate but you'll at least > know that demands are being made over and above the static > current, and your PSU will have to cope with that. Usually a > large reservoir capacitor will do. Reckon on about 1000uF > per amp at the minimum >=20 > As an example, infra-red transmitters, eg remote controls, > have a reservoir cap local to the LED(s). Remove that and > it doesn't work so good, yet to all intents and purposes the > circuit looks the same to a DMM. That cap is there to supply > the IR pulse demand Thanks. This correlates with the advice others have offered on this thread. I do plan to make all these tests, but I have yet to do so. I will report back on my findings in the next few days. All the evidence now seems to fairly strongly point to the whimpy ability of the chosen wall wart to supply power to the tapestry LED display as a replacement for the AA alkaline batteries. Regards, web... --=20 William Bulley Email: web@umich.edu 72 characters width template ----------------------------------------->| --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .