A quick question on relays
{With my specified input} can I use the "Sainsmart DC 5V Relay Module for Arduino PIC ARM DSP AVR MSP430 TTL Logic" board 


Yes.  A low level input WILL operate this OK as long as it can provide enough current to operate the optocoupler. See below 



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The circuit diagram is shown below.
 A low level input WILL operate this OK as long as it can provide enough current to operate the optocoupler.
 Sainsmart may be able to advise how much current is needed.
 10 mA is usually enough - occasionally more is needed and sometimes much less.
 R14 may need to be changed.
 The Vcc changed would ideally be the same voltage that you say is 3-5V so that there are no pronblems when the input is high.