NPN NO proximity sensor resistor enquiry

[marbles]

Hi,

I am planning to use proximity sensors for my home and limit switches for Mach3. NPN NO sensors. They will be supplied by 24v going to a generic 5 axis board ( 5v)

Am I correct in thinking that means the black wire to the BOB from the sensor will also be receiving 24v, which will potentially damage what is a 5v board?

If thats the case should I not add a resistor somewhere to lower the voltage from 24v to near 5v to the BOB?

Any info or links most welcome.

Thanks.

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[marbles]

Proximity spec

Set up distance 0 - 3.6mm
Detection objete Magenetic
Effective voltage DC: 12 - 24V AC: 110 - 220V
Detection distance 4mm± 10%
Response frequency DC:0.5kHz
AC:25Hz
Working voltage DC:6 - 36V
AC: 90-250V
Control output DC: NPN / PNP:?300mA DC 2 wire:?200mA
AC :400mA
Loop protection DC :reversal connection protection protection, surge avsorption ,load short-circuit protecrion
AC : surge avsorption



BOB

[john-100]

with the BOB in your photo you don't need the pull up resistor shown in the diagram



John

PS

[marbles]

Excellent info thanks!

Just out of interest is the db25 1205 BOB also optoisolated for the same proximity sensors?

[john-100]

yes
the 5 inputs to the PC printer port (or motion controller ) are opto-isolated

the 12 printer port outputs are not isolated but they are buffered by two 74HHC245 IC's that ensures there is enough current drive
to the opto-islaters inside the stepper drivers

note-
the limit switch common is connected to the PWM 0-10V analogue spindle comtrol common

so you will need to ensure the spindle speed control VFD you use has an input that is isolated from the mains

John

[ericks]

I have the same bob....just be aware that the lm317 gets quite hot when you use 24 V

[marbles]

note-
the limit switch common is connected to the PWM 0-10V analogue spindle comtrol common
so you will need to ensure the spindle speed control VFD you use has an input that is isolated from the mains

John

Now thats interesting! The GND pin suggested to use as the common on my blue board doesnt seem to work so i'm using the GND next to the 5V in. Good point about limit switch common is connected to the PWM 0-10V analogue spindle control common, I didnt know that.

I'm using a less well known VFD, an XSY-ATI. No idea about the isolation, the BOB is wired to the VFD on the control side. Spindle ON/OFF is fine but speed not working in Mach3? the two things might be connected.

[marbles]

I have the same bob....just be aware that the lm317 gets quite hot when you use 24 V

Good to know. Perhaps it would do not harm to add a 3.3k resistor, which would take the voltage down to around 5.8v or something. The Im317 would like that

[ericks]

I am just using 12 V, you don't want less than 12V! Your pwm to voltage converter requires more than 10 V

[marbles]

I am just using 12 V, you don't want less than 12V! Your pwm to voltage converter requires more than 10 V

Ah right your talking about pwm to voltage convertion. More than 10v. Gotcha!

[john-100]

If I converted my mini lathe with a spindle motor speed control more like this KB electronics board or a clone



the entire circuit board is live
and you need a BOB with a PWM to analogue control that is isolated from the rest of the BOB

some thing like CNC4PS's C6


John

[marbles]

the entire circuit board is live and you need a BOB with a PWM to analogue control that is isolated from the rest of the BOB
John

Ok good point. I need to look into what the both BOB's I have are fitted with. At the moment I am wired to the VFD as per the image below.