How can I make .5VDC into 9VDC?
Answer:
Do you have access to a separate power source or is all the energy to drive the relay supposed to come from the 0.5V source?
If the latter then you need to make boost converter. Your problem is that 0.5 volts is barely enough to drive anything. The diode drop on a normal silicon NPN transistor is around 0.7V.
You need to build an oscillator that runs at low voltage. You should probably start looking for transistors that can be turned on. Low threshold FETs come to mind. A quick googling give the following example. http://www.discovercircuits.com/h-corner...
With an oscillating signal you can implement one of many boost configurations. Since you know you have 0.5V, you could simply put it through an up transformer and then rectify and smooth the output.
If you have a separate power source, then life is easy. Use the 0.5 volts to switch on a low turn on threshold transistor that switches in 9V. Put in suitable protection (diodes) to deal with the back EMF of the relay.
You can build a little op amp circuit (transistor) to do this. Since you stepping up the voltage though, you're current will drop.
The answers post by the user, for information only, FunQA.com does not guarantee the right.
More Questions and Answers: