Hey guys,
I'm working on a new project that has me scratching my head.
The circuit controls two 12v winches, using PWM to get them to sync. In fact the two winches are pulling on a tilting solar panel array to track the sun. At horizontal they move the same amount, but as it tilts more one way then one winch needs to turn further.
But here's my concern. I've got about 30 ft of 6 ga wire from the battery to the control circuit, and another 10 ft to the winches. These winches draw about 30 amps. I may only be pulsing in the 50 hz range. But when that FET turns off, I'm going to still have 30 amps coming down that wire causing a monster surge on both the +12v and ground wires.
My concern is that my 3.3 regulator will struggle to protect my microcontroller. It will also require higher voltage tolerant FETs, or possibly even activate the FETs due to the surge.
For protecting the regulator, I'm thinking of a 22 ohm resistor followed by a 15v zener diode and capacitor. Let's say my 3v logic draws 50mA with some LEDs, that's a whole 1v drop across the resistor (burning only 50mW power, so a 0805 or 1206 resistor will work there. Go the other direction, let's say I have a 30v surge. That will drop about 15v across the 22ohm resistor, wow, 10 watts! And nearly an amp, but this is a short pulse. I'll make sure the resistor is rated for the current.
But what if the surge is 50v, or 100v? Anyone have any guidance? I can't get the battery closer, I have 3 towers sharing one battery. And the winches will cycle very little, maybe every 15 minutes for a couple of seconds. And I can slowly move the pivot back at night to return to morning position.
I'm working on a new project that has me scratching my head.
The circuit controls two 12v winches, using PWM to get them to sync. In fact the two winches are pulling on a tilting solar panel array to track the sun. At horizontal they move the same amount, but as it tilts more one way then one winch needs to turn further.
But here's my concern. I've got about 30 ft of 6 ga wire from the battery to the control circuit, and another 10 ft to the winches. These winches draw about 30 amps. I may only be pulsing in the 50 hz range. But when that FET turns off, I'm going to still have 30 amps coming down that wire causing a monster surge on both the +12v and ground wires.
My concern is that my 3.3 regulator will struggle to protect my microcontroller. It will also require higher voltage tolerant FETs, or possibly even activate the FETs due to the surge.
For protecting the regulator, I'm thinking of a 22 ohm resistor followed by a 15v zener diode and capacitor. Let's say my 3v logic draws 50mA with some LEDs, that's a whole 1v drop across the resistor (burning only 50mW power, so a 0805 or 1206 resistor will work there. Go the other direction, let's say I have a 30v surge. That will drop about 15v across the 22ohm resistor, wow, 10 watts! And nearly an amp, but this is a short pulse. I'll make sure the resistor is rated for the current.
But what if the surge is 50v, or 100v? Anyone have any guidance? I can't get the battery closer, I have 3 towers sharing one battery. And the winches will cycle very little, maybe every 15 minutes for a couple of seconds. And I can slowly move the pivot back at night to return to morning position.