as your saying there will be dips in current as both the motors draw current , can i take 2 250v to 12 transformers each giving out 12v 2 amps and connect them in parallel to make a 12 volt 4 amps psu ? sorry i know this is stupid question but just wanted to know . and will using higher amps make the capacitors explode?
The problem with many examples on the web is that they don't always follow up.
We see so many examples of that in this forum where a link is given but the OP has an issue in some form with the exact same project.
The advice given in here is often based on ACTUAL experience, facts, etc.
None of us want your project to fail.
Quite the opposite, we want you to be happy with your project and it may give you some valuable experience in taking on other projects.
I only use 24 volt or 36 volt here and all rated at 10 amps or more.
The V3 shield if most often rated up to 24 volts unless you get one that does state 36 volt.
If you check the caps on the shield they will tell you the voltage they are rated for.
The amps will not normally kill the caps in any way.
That would be the least of any worries.
sir i have no doubt that you are experienced , if i had i wouldnt come here even this was my last resort and you have helped me understand the plotters electronics better as im a complete begginer . my cnc shield v3 is rated for upto 36 volts .
i wanted to ask
is it possible to make higer amps psu by using multiple 250 to 12v transformers in parallel?
You can but they will need to be both the same supplies in terms of voltage and current.
There will also need to be diodes in the circuit to prevent back voltage.
It would also be prudent to add an LED+resistor on each supply so you know both are working and not just one.
Adding capacitors across the output would give it some added benefit just before the load.
thank you
What have you set the motor current to?
In the instructional video for setting up the DRV8825 drivers on the Pololu website it demonstrates that the supply current to the driver is considerably lower than the coil current which you set up. This is because the drivers act as a "buck down converter", stepping down the voltage and stepping up the current. I recommend finding the video and viewing it right through. The higher the supply voltage the lower the supply current. I use GRBL with DRV8825s with a 24V 2A PSU driving up to 2 NEMA23 steppers and it works just fine. Note also that you don't have to set the current to the rated max for your motors, you only need enough current to get the torque you need.
For testing, it's easy to drive GRBL from the serial monitor - you type into the command line at the top and see the response from GRBL in the main window. This removes UGS from the equation.
yesterday i got the motors to work somehoe and im conformed nothing is damaged , until i get a multimetre i cannot proceed , and i will also have to arrange a suitable psu before proceeding with any more testing.
today i got a multimeter and i adjusted the drv8825 vref to 0.74 ~0.75 amps as my motor rating for single phase is 1.7 amps , i took 1.5 amps as rating instead to not damage the motors . now something weird is going on
at the moment i dont have 12v 10 amps psu
i have
-
12 v 1 amps psu -
12v 2 amps psu -
12v 3.3 amps psu
when i connet the cnc shield to 12v 1 amps psu , everything works just fine (i have no idea how )
but when i connect it to 12 v 3.3 amps and 12 v 2 amps psu it dosent work .
question 1
could this mean the other 2 power adapters are damaged ?
and btw dont worry i wont be using the 12 volts 1 amps psu for a complete build , im just trying to be safe as the last time my capacitors blasted for some reason . thats not a problem now as i replaced them .
question 2
is there any way to check weather a power adapter is working as expected using a multimeter?
okay guys , I solved this problem , for anyone who has the same issue can refer to this , hope it helps
just like anyone would , i have used adapters that were lying around the house , didn't know if it worked or not , i checked with a dc motor and all of them worked but don't be fooled by it , u must check with a multimeter to be sure
to do this , plug in the ac adapter to wall socket
set the multimeter to dc 20 v as its the closest to 12 volts
bring + and - of the adapter in contact with + and - of the multimeter .
if the reading is very close to 12 volts like 11.98 ~ 12.5
then your adapter is good
but if you get readings that are negative (reversed polarity )
then its bad
one of the adapters i tested which was bad , gave readings of 15 volts , so i guess even if that happens , you should know the adapter is bad
correct me if I'm wrong on this part
Sorry, but you are wrong. The adapter rated voltage should be the voltage when the rated current is being drawn from the adapter. You are testing an adapter with ZERO current being drawn from the adapter. Not all adapters are the same. Some will automatically hold the voltage near the rated value others, like your 15 volt one, will not correct the voltage with no load. Likely that one is a transformer and rectifier adapter,and the others are electronically controlled.
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noted it , thanks.
im having the same issue as CNC Shield V3 Servo Problem, i already have 2 cnc boards and the servo dosent work in any of them , are both my cnc shields faulty?
Please try after uploading a different version of grbl to your board.
i have version 9
Please try laser grbl or servo grbl.
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