Hello,
I am wondering if it is possible to use a larger, commercially available push button with an Arduino instead of the tiny breadboard buttons that are typically used. I have attached a link to a type of switch that I have in mind to give an idea of the switching current advertised(~5A, 24VDC), and I know that the Arduino pins can't provide anywhere near that. The buttons available from this supplier go as low as 1A, but I would prefer to use something like the one linked if possible
The ratings on a switch are it's maximum ratings so it's OK to use it with the Arduino.
Now, if you are actually going to switch 24V / 5A, then we need to know how the Arduino fits into the picture because the Arduino can't handle that directly.
Fundamental misunderstanding of that specification then. Basically Arduino is controlling several motor actions(motors have separate power supplies and driver's) that I want to initialize with the push of this button.
[Arduino waiting, reading button state]->[oh boy, button press detected]->[tell motors to do stuff]
armorall20:
Fundamental misunderstanding of that specification then. Basically Arduino is controlling several motor actions(motors have separate power supplies and driver's) that I want to initialize with the push of this button.
[Arduino waiting, reading button state]->[oh boy, button press detected]->[tell motors to do stuff]
You can control an Arduino pin with the smallest. weakest switch imaginable. Well, perhaps not that small.
What you do need to spec is the relay or other method to control the power going to the motors.
Paul
Paul_KD7HB:
What you do need to spec is the relay or other method to control the power going to the motors.Paul
Do I need to use relays in addition to the motor drivers? I was under the understanding that the wiring would be [power supply]->[motor controller/driver]->[stepper and DC motors, one being as high as 8A/phase]with the Arduino simply sending commands to the driver, therefore insulating the Arduino from the large source of current in the system. I would imagine the power supply units we are using have some sort of onboard relay to protect the electronics
armorall20:
Do I need to use relays in addition to the motor drivers? I was under the understanding that the wiring would be [power supply]->[motor controller/driver]->[stepper and DC motors, one being as high as 8A/phase]with the Arduino simply sending commands to the driver, therefore insulating the Arduino from the large source of current in the system. I would imagine the power supply units we are using have some sort of onboard relay to protect the electronics
What motor drivers? Why don't you tell us the whole setup you have instead of telling it in tiny bits each post?
Paul
armorall20:
I am wondering if it is possible to use a larger, commercially available push button with an Arduino
The shocking answer is: NO
(not always)
Surprisingly, switches designed for high voltages and currents may stop working quite quickly if you just wired 'em into a 5V low-current sensing circuit.
Switches have a "Minimum Applicable Load" below which the failure rate increases, the data is quite difficult to find tho. OMROM call their switch contact blocks 'Microload' which you can sense at 5V 1mA. It also depends if the switch is simply push-to-make, snap-action, wiping contacts and so on.
Generally, if the body is fully sealed, and contacts are silver (or better) you can use 5V but make sure you pass around 20mA.
Yours,
TonyWilk
Paul_KD7HB:
What motor drivers? Why don't you tell us the whole setup you have instead of telling it in tiny bits each post?Paul
PS:PMT-24V200W1AM Delta Electronics | Mouser Europe
All drivers and PS are similar or identical to these. Basically a wall outlet feeds the power supplies, which will feel the Voltage In for each of their respective drivers. These drivers will then drive their respective stepper motors. The arduino will be powered by one of these separate power supplies that will supply the correct voltage to run the arduino. Since the PS current is not passing through the arduino before it goes to the motor drivers, I did not see a need for a relay, but I am inexperienced in this and could be incorrect. To my understanding, a relay would be used if I wanted to switch the power to any of these drivers on/off, but I figured that few extra lines of code seemed unnecessary.
TonyWilk:
The shocking answer is: NO
(not always)Surprisingly, switches designed for high voltages and currents may stop working quite quickly if you just wired 'em into a 5V low-current sensing circuit.
Switches have a "Minimum Applicable Load" below which the failure rate increases, the data is quite difficult to find tho. OMROM call their switch contact blocks 'Microload' which you can sense at 5V 1mA. It also depends if the switch is simply push-to-make, snap-action, wiping contacts and so on.
Generally, if the body is fully sealed, and contacts are silver (or better) you can use 5V but make sure you pass around 20mA.
Yours,
TonyWilk
The same vendor as original post also carries what they call "low-voltage" switches. Would these options be better in the long term for use with an arduino?
I would not be completely opposed to the OMROM switches that you mentioned if they will be significantly better in the long term, just not crazy about the appearance of them.
The relay response was because all you wrote was you wanted to "control" the motors. What does that mean other than off/on. Thank you for elaborating. All should work. Be advised the ratings of Chinese power supplies may be one or the other, but not both voltage and current max at the same time. Experience!
Paul
armorall20:
The same vendor as original post also carries what they call "low-voltage" switches
snip
Unfortunately those links just redirect to their general 'push button switches' page, I did look for "low voltage" switches, but they give no information about them.
Might be better off looking at Digikey, Mouser or Farnell... they all have billions of different switches (I may exaggerate slightly)
A couple of random examples:
These are sealed, gold contact things: APEM Pushbutton , C&K SWITCH PUSH SPST
And an Omron one you don't like 
... omron switch
... is notable for the datasheet actually saying: "Minimum applicable load: 10 mA at 5 VDC"
Having said all that... if this is for a project of yours for use in a nice clean, dry room it's a lot different from some industrial setting where the environment damp and/or dirty and long-term reliability is really important - so don't get too hung up on it.
Yours,
TonyWilk
TonyWilk:
Unfortunately those links just redirect to their general 'push button switches' page, I did look for "low voltage" switches, but they give no information about them.Might be better off looking at Digikey, Mouser or Farnell... they all have billions of different switches (I may exaggerate slightly)
A couple of random examples:
These are sealed, gold contact things: APEM Pushbutton , C&K SWITCH PUSH SPSTAnd an Omron one you don't like
... is notable for the datasheet actually saying: "Minimum applicable load: 10 mA at 5 VDC"Having said all that... if this is for a project of yours for use in a nice clean, dry room it's a lot different from some industrial setting where the environment damp and/or dirty and long-term reliability is really important - so don't get too hung up on it.
Yours,
TonyWilk
Thank you very much for your detailed and helpful responses. This project is going to find itself in an industrial setting(we are college students designing and making the prototype for a company for our senior (mechanical engineers, hence the base-level electrical questions) project), so yes, long term reliability is important to us. Outside of these examples, is there any specific trait or material that I should look for when selecting a switch? You noted "sealed, gold contact" and the OMROM specifying the minimum applicable load. Is there anything outside of these that should be paid attention to?
armorall20:
This project is going to find itself in an industrial setting snip
Ah, ok. Off the top of my head then...
a. don't buy cheap crap from eBay, AliExpress, Banggood.... :
b. Look for a datasheet on the switch from the actual manufacturer (this is where McMaster's not good)
c. already mentioned: for "logic switching" (5V, a few mA) you want the switch sealed and with nice contacts, preferable gold flashed.
d. For small pcb 'clicky' buttons and the like, switching to GND and using, say, 10kohm pullup to 5V (or the pullup on an Arduino input) may be fine... but (unless it specifically states in the data sheet) panel switches will need something like a 220ohm pull-up to give a switching current of ~ 20mA.
e. If it's an industrial control panel on a machine and the 'brains' are somewhere else, consider using 12V or 24V to power your panel switches and sense the current at the processor with an optoisolator. (i.e. generally, don't run wires to 5V switch inputs outside of a cabinet - especially if there's other electrical stuff going on.)
Yours,
TonyWilk