using +5 on the protoboard
dr hydra
Posts: 212
I have an old propeller proto board #32212 (not the usb type). I am going to using it with a 5v microcontroller (MEGA32). Can I power the MEGA 32 from the +5 hole on the proto board? Is the +5 hole a regulated power supply? Will the servo interface cause any problems?
Comments
So yes, the +5 hole could be used to power the other uC but there are additional 5V holes near the regulator. There are also Vss and 3.3V holes available.
I don't think the servo interface would cause a problem but you'd too to just the +5 hole to the center hole to provide the servo interface power.
The servo interface has an additional inductor on its power line. I assume the inductor is there to reduce noise.
The servo interface isn't connected to any of the Prop's I/O pins. You need to provide a connections yourself to the holes just outside of the servo interface boxes. (Not that you'd need this to power the other uC.)
IIRC the 5V regulator is good for over 100mA on the Proto Board.
The servos have a special power bus that is switched on by the third position of the slide switch, while the other +5 is not involved with the servos.
And the servo power bus adds other complications as it has a big capacitor involve, AND the choice to have it operate from an independent power supply.
Take a good look at the Proto Board documentation and probe the power that is available near the top edge of the board. Nothing will make it as clear as using a VOM and locating all the +5 on the board.
As an example, let's say, a board has the 3.3v regulator and the regulator is rate at 500mA MAX. Could a propeller chip and its serial EEPROM, and let's say a PIC24 run off the same power supply? How do you check...do you add all the volatage rates together for each device and how much is the max current for the propeller or the PIC24? And what happens if you exceed the MAX amount for the regulator..does it damage the chips or the regulator? Or is it like a dead batttery?
Lots of current will cause lots of heat, but even that's ok up to a point if a heat sink can disparate enough heat to keep the temperature down. But if the regulators get too hot, you will start to have problems.
Some regulators have internal thermal shutdowns, but if your circuit draws enough current to cause that then it really needs fixing, even if the shutdown has protected the regulator. Also, high temperatures will shorten the life of most electrical parts, even if they don't fail immediately.
Every regulator chip I have seen has thermal protection built in, so there is almost no chance of damaging the chips or regulator. The regulator will usually shut down until it cools off and then turn back on. This on/off cycling can happen several times per second so it can cause problems to mechanical systems (motors, solenoids, etc.) that are controlled by the chips the regulator is powering.
Correct.
This may sound like nit picking but when the Vss from two supplies are connected together they should really be referred to as the "common" connection unless they are connected to an actual ground at some point. In most cases this is not an issue, but if two or more modules with their own regulators are connected and used in a circuit that is floating on an AC or DC voltage they are not connected by or to ground.
Thank you for the help...I am not sure I fully understand the your response about 'ground' and common connections. I thought ground was ground, but as long as I am able to use two power supplies and two 3.3 regulators connect the grounds (or common connections) and both chips will work, I am fine.
I think technically "ground" has a path to the dirt in the ground under our feet. I think a metal pipe driven into the ground (as in dirt) is often used as a ground for a building's electrical system.
I read there's debate on whether or not connecting the metal housing of an appliance to this ground connection (often the third hole in an AC outlet) is really a good idea.
Also, we have electronic devices - like dual voltage op-amps where the common (which is often referred to a ground) sits between a plus voltage and a negative voltage. So if you have a power supply for an op-amp, it might be +12 V, 0 Volts, and -12 volts without any real world connection to anything outside.
And if you do try to connect it to the AC mains ground connection, it might by--pass the isolation created by a transformer and actually become a serious shock hazard.
I guess all this is a complicated way of saying that one should be sure not to think everything that is labled 0 volts is safe to connect to the grounded side of an AC Mains. Things might burst into flames or people might be knocked dead. In an isolated power supply (either by a good safe transformer or a battery power supply) the 0 volts might float above or below a real ground and work fine.
All the 0 volts should be connected together so a common reference of 0 is created. That will make the digital 0's and 1's properly interpreted. It may also eliminate some noise problems.