electronicsfreak
Member
Attached to this message is a circuit schematic of the device as well as the device itself. What it is isa motor control drive board utilizing a PIC for a project that I've been working on for quite a while now. The board works and properly functions for a little bit until at random it seems to just "shut down". Now because of how it would function and then break down gave me three seperate thoughts on how it could be failing, which are :
The LM317's are heating up and eventually shutting down--not the only case as they didn't always heat up when it shut down,
the LM317's arent able to supply all that the 13 seperate motors require--could be and I was referred by a friend to try and increase the capacitance of the capacitors that are attached to the output leads on the LM317's, and
the Motors are drawing too much current from the PIC which causes it to shut itself down. --this is what I"m here for, because when I designed the circuit and chose part values, I was following the datasheet for the required current instead of the motors actual internal resistance/voltage of the circuit (with the datasheet, .7A with the resistance, 2.3A!!) and just lowering the base resistor value of each transistor would go WAY over their rated collector current. I was suggested by my friend that I could relace all of the npn transistors on the board with a MOSFET N type transistor. Only one problem. Other than they are controlled by voltage (from a few online tutorials) I don't know anything else about these things.
so here's my question. Does anyone know of a MOSFET that could fit the parameters required that I could replace the NTE-123A's with (that's what the npn transistors are), how I would calculate the base resistor value (if needed), and do they make MOSFET transistors that are in a case style close to the size of a T092 or a T039? -(if not, then just one that I would be able to swap into the board that doesn't take up very much space--anything at or under the size of a T0220)
any help would be appreciated. Thanks.
--note, as I realize that they do make h-bridges that would replace both the relays and transistors here, I am not at a point where I could do a complete swap like that.
The LM317's are heating up and eventually shutting down--not the only case as they didn't always heat up when it shut down,
the LM317's arent able to supply all that the 13 seperate motors require--could be and I was referred by a friend to try and increase the capacitance of the capacitors that are attached to the output leads on the LM317's, and
the Motors are drawing too much current from the PIC which causes it to shut itself down. --this is what I"m here for, because when I designed the circuit and chose part values, I was following the datasheet for the required current instead of the motors actual internal resistance/voltage of the circuit (with the datasheet, .7A with the resistance, 2.3A!!) and just lowering the base resistor value of each transistor would go WAY over their rated collector current. I was suggested by my friend that I could relace all of the npn transistors on the board with a MOSFET N type transistor. Only one problem. Other than they are controlled by voltage (from a few online tutorials) I don't know anything else about these things.
so here's my question. Does anyone know of a MOSFET that could fit the parameters required that I could replace the NTE-123A's with (that's what the npn transistors are), how I would calculate the base resistor value (if needed), and do they make MOSFET transistors that are in a case style close to the size of a T092 or a T039? -(if not, then just one that I would be able to swap into the board that doesn't take up very much space--anything at or under the size of a T0220)
any help would be appreciated. Thanks.
--note, as I realize that they do make h-bridges that would replace both the relays and transistors here, I am not at a point where I could do a complete swap like that.