Hi guys i am slowly working towards having my own board built utilizing the ATMEGA 328P-PU Chip and need some help with my power supply. This is going in my truck and as of now i am using a 100uFcap to a LM7809 Vreg then a 10uF Cap to the LM7805 Vreg then a 1uF cap then on to the chip. Is there a better way of doing this? I would like it to be a small as possible to reduce the overall size of my PCB.
Would the capacitor before the voltage regulator not absorb most of these spikes? I think a basic lm7085 would get too hot dropping 14V down to 5V dont you think? I want to keep this as small as possible but reliable as well. The components must also be rated to operate in -40C temperature as this is going in my truck permanently and it gets pretty cold here in Canada. Would a switching voltage regulator be a better option? I have heard of them but never used one nor do i know much about them.
If my prototype goes as planned I might take this to production as i have a few people interested in it so i want this to be as proffesional as possible. I do like the simplicity of the lighter socket idea but i dont think it would be the right choice for this.
If you intend to distribute your product then a suitable automotive electrical noise and spike protection circuit is absolutely required. Polarity reversals (e.g. during jump starting) and spikes of hundreds of volts are occasionally encountered in automotive electronics. You can buy surge protection chips or build your own. I've attached a document describing the hazards as well as a DIY circuit that I've found useful (after frying some of my own electronics in a vehicle). In the circuit, that 1.5KE18 Zener diode is a 1500 watt spike suppressor, and costs about $0.25 at Mouser. Of course a fuse should precede it. The circuit also protects against polarity reversal and reduces radio frequency noise.