Hello! I want to apologize a head of time because I am very new to circuitry.

I am working on a laser etcher that uses stepper motors from PC disk drives for the X and Y axis, and a small laser. When each of these components is hooked up on their own, the work great. But when I hook all three up together, the steppers really struggle and the laser doesn't light up at all.

I am using a:
12v 2Amp power supply
1000uf 16v capacitor
250mW laser
2x A4988 stepper motor driver modules
Arduino Nano (powered by computer via USB cable)



If you need any more information, feel free to ask. Thanks in advanced!

-Kaleb

 

can you show us a picture of the actual set up please

the likely reason is the ground bounce or the psu dropping due to load,

 

Hello,

Why not power the steppermotor controller boards from the 5 Volts for the laser in stead of the arduino?
It can be the power from the USB is to short.

Bertus

 

So, replace all the 5v connections from the Arduino to the steppers with the 5v from the voltage regulator?

 

What is that thing dangling off the bottom right corner of the schematic? It looks like a battery cell. If so, when the MOSFET switches on it looks as though the cell and the LM7805 output will be shorted to ground.

 

Thats actually the laser

 

When it all goes weak, measure the voltage of the 12V supply. If it's less than 12V then you need a supply capable of more than 2A.

 

By now you should have taken the hint and checked the power supplies. My first boss in the electronics industry once told me "First thing, check the power supplies." because if that isn't right then you can't count on anything else being right either.

 

After checking the power supplies at the supply, check the voltages at the load. Inadequate conductors and poor connections will cause a whole lot of problems. AND, the grounds should all have a "star point", one common connecton point with an adequate connection to the supply negative. If the individual modules are OK but the whole system does not work right then the problem is power distribution.

 

How do I figure out how many amps I need? Will too many burn the circuit up?

 

Measure the current for each part individually and add up the measured values to give you the total requirement.

The supply voltage should be correct and the available current should be greater than the total requirement. It doesn't matter how much greater the current is, the circuit will draw only what it needs.

 

How do I figure out how many amps I need? Will too many burn the circuit up?

Power supply current capability does not mean the amount of current that the loads will take.
The way to determine the current requirement is to add up the current requirments of all the individual items.
But we have no information about the total current required and so we have no means of knowing the current needed.

 

If you want to be sure you're safe, check the datasheets and get the maximum current requirement for every device. For the servos this will be the stall current. Add them all up and get a power supply that will give you maybe 25% more than your total max value. If only one servo will be operating at a time then only include the stall current once, but if all will be operating simultaneously then add them all up. Now you'll be 100% sure that your power supply wont' be the weak point, and since it shouldn't be operating at anywhere near its max under normal conditions it should last a very long time.

 

Measure the current for each part individually and add up the measured values to give you the total requirement.

The supply voltage should be correct and the available current should be greater than the total requirement. It doesn't matter how much greater the current is, the circuit will draw only what it needs.

After finding a new power supply with more amps, all of the components work great. So, the power supply was my problem. Thank you all for you help!