18VDC Circuit design help

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RuthlessKarma

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I could use some help with a circuit design that can provide simultaneous power at 12VDC @ 1A to a wireless router, 9VDC @1.25A to a webcam, 12VDC @ 500mA to an Arduino, and 12VDC @ 1A to each of TWO small motors.I am using a 18VDC @ 3.9Ah battery as a source. I think my current scheme of voltage regulators and capacitors wont allow for enough current. I may be in over my head. Any help would be appreciated.
 
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Lessee: 1 + 1.25 + 0.5 + 1 + 1 = 4.75A. Looks like you're already over budget here, even with down-conversion (you meant to write "3.9 Ah", right?).
 

hi,
Is it really a 3.9mAh battery..?
 
i believe you meant 3.9Ah, well the battery will work only that it wont last longer than an hour.
 
Can you get 2 batteries? Connect them in parallel, you should get just over 1.5 hours of life. If noise is an issue, I would recomend a seperate power supply for the motors. Is this for a robot? Battery+Webcam+uC+motors= a robot but the rouder dumbfounds me...
 
You are correct, the battery is 3.9Ah. It is for a robot to be controlled via internet (hence the router). I am willing to sacrifice a certain amount of battery life because more Ah means more weight. I haven't reached the point of knowing wether or not noise will be an issue, as my power supply circuitry does not work in its current configuration.
 

hi,
Have you actually measured the current drawn by the individual modules in the project.?? also the total worst case current draw.???
 
No I have not. I got the current ratings from the wall warts of each device. I just thought it best to try to duplicate that output as closely as possible.
 
The battery will output the current needed to operate each device but the lifespan will be dramaticly shortened. As for the regulation, you can use an op-amp regulator for the motor supply to reduce circuit noise while using a standard voltage regulator with a current boosting transistor for each of the other outputs respectively.
 
These are so cheap you could probably use 2 or 3.

**broken link removed**
 
ebay makes everything over priced in my oppinion. Although a step down converter would work pretty well for this aplication.
 
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