Hi, this is my final project for my bachelor. hope you guys can help in some matters.
My project consists in a 6v 3,7w solar panel to charge different types of batteries/devices, wich are: lipo battery, usb devices and 4 AA nimh abtteries.
Also i'll be using a pic16f648a to control and monitor each circuit (voltage/current), turn on and off each circuit and display info on LCD. i'll be using 4 AA 2300mha batteries to power this last part.
I have several questions/doubts regarding all this. Also try to keep it simple, im not such an expert Any tip/criticis welcome! So:
Nimh charger: Im using a current limitter circuit (500ma +/-) with lm317.
Q: First thing i would like to know is if lm7805 has less voltage drop than lm317 because i.e. for Nimh charger i will need 5,6v output (to charge nimh to 1,4v each) and with lm317 im getting 5,52v. i need at least 5,6v so then microcontroller could shut off the circuit.
USB charger: For this one im using voltage limitter (5.15v +/-) again with lm317 and current will depend on the load.
Q:but for i.e. Iphone charges by usb at 500ma but because usb's (laptops etc) are limitted to this current, while charging from "wall" it charges up to 1A. so in my circuit iphone will draw as much current as it can get. Am i right? therefore the voltage output from solar panel will be lower wich will make lm317 Vout also lower since im already on thresold input voltage (6v) for lm317 to give me 5.15v. im missing something here. any tips?
Now comes the second part of the problem
as i said im using pic16f to switch on and of each circuit. i've been reading a lot about what switches to use and i cant decide. im between transistor and relay combination, transistor (2n222) to power transistor (tip32c/tip117) or only adequated power transistor (read a lot of datasheets). Main thing here, the less voltage drop, the better!! i bought finder D06 5v relay,measured the resistence in the "switch" itself and has 0.3Ω
wich gives me for the max current panel can draw a 0.18V max drop. i think its quite good, anyway i wonder if there is any transistor that is a better solution i came across 2n222 transistor but Ic (collector current) is 0.6A max so in a very shiny day solar panel will draw more than that. Any tips??
Last thing, and as curiosity. 16f648 has inbuilt 4Mhz clock is this good enough for this monitoring i desire? (i think it is for its simplicity) i wanna hear your opinion about this. Also because i never know when to use higher one and what value should be good for any given project.
Many thanks!!! if you need any extra info, data etc. just tell me what
My project consists in a 6v 3,7w solar panel to charge different types of batteries/devices, wich are: lipo battery, usb devices and 4 AA nimh abtteries.
Also i'll be using a pic16f648a to control and monitor each circuit (voltage/current), turn on and off each circuit and display info on LCD. i'll be using 4 AA 2300mha batteries to power this last part.
I have several questions/doubts regarding all this. Also try to keep it simple, im not such an expert Any tip/criticis welcome! So:
Nimh charger: Im using a current limitter circuit (500ma +/-) with lm317.
Q: First thing i would like to know is if lm7805 has less voltage drop than lm317 because i.e. for Nimh charger i will need 5,6v output (to charge nimh to 1,4v each) and with lm317 im getting 5,52v. i need at least 5,6v so then microcontroller could shut off the circuit.
USB charger: For this one im using voltage limitter (5.15v +/-) again with lm317 and current will depend on the load.
Q:but for i.e. Iphone charges by usb at 500ma but because usb's (laptops etc) are limitted to this current, while charging from "wall" it charges up to 1A. so in my circuit iphone will draw as much current as it can get. Am i right? therefore the voltage output from solar panel will be lower wich will make lm317 Vout also lower since im already on thresold input voltage (6v) for lm317 to give me 5.15v. im missing something here. any tips?
Now comes the second part of the problem
as i said im using pic16f to switch on and of each circuit. i've been reading a lot about what switches to use and i cant decide. im between transistor and relay combination, transistor (2n222) to power transistor (tip32c/tip117) or only adequated power transistor (read a lot of datasheets). Main thing here, the less voltage drop, the better!! i bought finder D06 5v relay,measured the resistence in the "switch" itself and has 0.3Ω
wich gives me for the max current panel can draw a 0.18V max drop. i think its quite good, anyway i wonder if there is any transistor that is a better solution i came across 2n222 transistor but Ic (collector current) is 0.6A max so in a very shiny day solar panel will draw more than that. Any tips??
Last thing, and as curiosity. 16f648 has inbuilt 4Mhz clock is this good enough for this monitoring i desire? (i think it is for its simplicity) i wanna hear your opinion about this. Also because i never know when to use higher one and what value should be good for any given project.
Many thanks!!! if you need any extra info, data etc. just tell me what
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