I saw the mcubed fanamp, and the problem is that it doesn't supply enough power to do what I want to do and the only US retailer that sells them is OOS. So anyone who's an electronics whizz please help me out on circuit design of one? I don't need manual standby controls like the mcube it just needs to have the output voltage = the input voltage, but the output just needs more amperage. Even my friend who has a bachelors in EE doesn't know what to do... says he only deals with digital circuits.
Power from a single USB port cannot exceed 2.5W. Therefore, to get, say, 1A of current, you need to convert the power to 2.5V so you still don't go over the draw limit of 2.5W. To stay at 5V but with more current is impossible without more than one USB port.
usb port? I'm not talking about the BigNG just the fanamp. U kno PSU supplies constant 12V, the mobo supplies anywhere between 6-12V, the fanamp provides whatever the mobo fan headers voltage is, but draws current from PSU, so you don't burn out the mobo. anyhooo I'm a mechie and have no idea where to start. So far I'm reading up on http://en.wikipedia.org/wiki/LM317 The LM317 the description states which sounds like what I want to do, but now I need to know how to precisely regulate the control voltage to achieve the same output. Basically I need to know how to make it so that whatever the control voltage, output voltage = control voltage. The motherboard will provide a certain voltage probably ranging from 6-12V, but fed directly into the control lead the output from the LM317 probably won't equal that. From my common sense and logic I think you'd need a transformer, or something to provide some sort of conversion factor that will give the necessary control voltage. Oh god I hope I'm making sense to someone. And anyone who's an expert please feel free to chime in anytime and correct me if I'm babbling about the wrong thing.
Sorry, I don't know where I got USB from. Strange. Do you know how much current and power the fan connectors normally put out? What you need to watch is the power output (ie watts) because you could have a lot or a little voltage and a lot or a little current depending on what circuit you make, but you'll always be limited by the amount of power the connection can supply.
it shouldn't matter how much the fan header on the motherboard is putting out, it's not powering the fanamp or the fan, it's just providing a certain voltage the fanamp can copy. So if the motherboard is providing 12V then the fanamp draws its power from the PSU and provides the fan 12V. If the motherboard is putting out 7V then the fanamp still gets its power from the PSU but puts out 7V to the fan. This is so the motherboard and software can control the fan without burning out the header cuz the fans require more amperage than the mobo can supply.
It's past midnight here, I have to be up at 7 for college and I'm definitely not an EE, but I can point you in the right direction before I go to sleep. I'd suggest looking at power transistors/FETs such as the .... uhhhhh (from memory) LM395.
here is a simple way to put the problem out. "I want to supply voltage X from a power source that can only supply Y amps, but I want to supply up to Z+Y amps, I ahve a 2nd power source that supplies 12V with Z amps how can I get it done" Drawings of circuits with any labels are like 9999999999999999999x more useful to me than descriptions as if you mention a component I most likely will have no idea where to put it in a circuit or how to wire it up to achieve what I want.
Perhaps this will help, since my own brain has proven itself worthless. <even more stupidity> I'm going to bed.
I gbraduated with a BSEE...and went right into programing, so it's been a while. But, IIRC, you can use a power transistor in parallel with the voltage reg to get more current. I *think* you connect the collector and emiter across the voltage source to lock that voltage, but I can't remember how the base gets biased. Hopefully, someone like cpemma comes along and corrects me
Here is a mcubed-type circuit using a LT1085. The LT1085 is a 3 amp, low dropout version of the LM317. +12 vdc PC PSU - 12 volts from the computer power supply. (like the yellow wire on a molex connector) MB fan input - variable voltage from the fan connector on the motherboard Output to fans - Variable + voltage to fans with 3 amp max. current The LT1085 must have a heat sink. The pin numbers of the LT1085 vary, depending on package style. See The Data Sheet for exact pin numbers.
