First, you don't "drop" amperage. A source can have a very high current capability and the devices connected will only draw from that source what they did.What is confusing is that you say you have a 9V source and your sonar device is 5V. How are dropping the voltage from 9V to 5V? Are you using a regulator? You can't just use a resistor.
You can't use a resistor to drop voltage for an active device. You need to use a voltage regulator like a LM7805. It will regulate 9V down to 5V.The problem with a resistor is that the voltage drop will depend on the current draw. Active devices have changing current draws. A regulator will maintain 5V regardless of current draw.
Do you have any recommended sites or books I could benefit from?
Quote from: llhetlet on Dec 10, 2011, 06:42 amDo you have any recommended sites or books I could benefit from?You want to be serious about electronics? Pick up a copy of Grob's Basic Electronics (any edition in the last 20 years will do). Read it, understand it, do the math. Then read it some more. Then do some more math. Yes, electronics - if done right - relies on more than a bit of math. Get used to it. Or burn up parts (and money) - your choice...