measuring board's total amp usage?

Hi all, I'm in doubt as to where to put the two sensors of my multimeter if I want to measure the total amp used by the mega2560. I have a suspesion (?) that some of my errors are rooted here. I use a large (12v 2A) external supply though ..

Put them in line with the supply. That is put the -ve to the +ve of your supply and put the +ve of your meter to the input of your system.

Hi Mike, How are you today?

I'll go do!

Make sure you start with your meter set to the HIGHEST current range.

AWOL: Make sure you start with your meter set to the HIGHEST current range.

Yep, that was necessary. The multimeter set at 500mA went off scale .. The problem about Mike's suggestion is, that "everything", including 3 drivers, a joystick and a relay is plugged into the 12V source ... or put another way, the board taps into the same source as the other units. I'm not sure about the relay, but at time of measurement none of the drivers were active. Mechanically my setup works, but I've encountered an odd program-error that could match a decay in board-functionality.

As for what the board can pull ... I've setup 3 bipolar stepper-drivers 5 buttons less than 10 leds a joystick with 2 analog out (added a 220 ohm to each) one relay one SDCard So far I can make things work together, but am I on the edge on what to expect the board to handle? I know .. it depends on how each unit is setup. ... adding input from a sensor that's called as often as each driver Step() seems to provoke a program-error. The sensor does not seem to contribute more than 1 or 2 mA.

It'll take a lot of work to provide diagrams of all units ..

The problem about Mike's suggestion is, that "everything",

That is not a problem that is what it is designed to do.

The problem if you want a separate reading of all your devices is that you have to break the circuit and insert the meter into each circuit individually. Physically this is much more destructive.

Hi Mike,
I’m hesitant on ‘touching’ the circuits because I havn’t found a good implementation of … not burning the coil-resistors. The new resistors I just changed got a brown-out again, but the driver and motor are unharmed.
It’s ‘nice’ to have a joy-stick that just works whenever you want to move the pen ‘by hand’ (vs. by code), but it tends to leave stepping in a ‘wrong’ phase. Anyway, I could use the button of the joy-stick as a quick ‘turn-on’-button … and hope that I’ll remember to turn it off after use. Or something more fancy since I hate to ‘have to’ do something else but a particular task at hand.

As for the current measurement I just did … It goes off scale on 500 mA, and shows ‘nothing’ on 10A. I’ll have to figure out what’s achtually using current (besides the board), when it’s in ‘passive’ mode. I’m very likely to sacrifice all the blinking led-indicators … they are not implemented well anyway. Or … I’ve been to school … I should /CALCULATE/ the darn thing.

Do you need to plug one of your meter probes into a different socket to measure up to 10 amps?

dannable: Do you need to plug one of your meter probes into a different socket to measure up to 10 amps?

Yes .. reminding me I see, that the probe should be moved as well. Thanks.

not burning the coil-resistors.

Well I am not sure you should have coil resistors in the first place. It is much better to try and get the voltage right in the first place. The motors run better as well.

If they get too hot then the power rating of the resistor is too low. Calculate I2 R to get the power in watts and then get a resistor rated about twice what you burn. As there are resistors in the circuit it is easy enough to disconnect one end and put your meter in line. Failing that just measure the voltage across the resistor and the power is = E2 / R

Hi Mike,

Well I am not sure you should have coil resistors in the first place. It is much better to try and get the voltage right in the first place.

I hate the principle of burning energy off in a resistor to get things to work right. I did have some attempts at start, and left with the impression, that I could not switch the analog-in on Enable fast enough.
I recently did find some code that sets pwm width and duration in hardware … if it responds fast enough I could use a much higher voltage and cut the duration in each step and maybe even think in terms of micro-stepping to give the motors a quiet hum instead of the bangbang when it’s not on max-speed.
I do know myself well enough to know that it will not be a left-hand job. And, it’s the motors that’s at the gunpoint in trial & error.
Maybe worst obstacle is: I’ve made myself a crucial component of a 3d-scanner … I’m dying to try it out.