Boxford TCL125. (Fresh start )

**Doddy** · 31-10-2020

John - firstly, these are usually infra-red, so it may well have been illuminated even if you couldn't see it (hint - you can often get a mobile phone camera live-view to witness IR LEDs).

Reverse voltage?, yup, a good way to fry an LED.

The good thing is these are generally fairly standard devices, although pin-outs may vary. And drive voltages?, can be pretty much whatever you need. I'll assume you've not hit this before otherwise you'd not be asking.. Take the supply voltage, and subtract the forward voltage drop of the LED. Then divide that by your chosen forward current. That gives the value of a resistor to place in series with the LED for it to operate at that voltage. That Datasheet indicated a max forward current of 40mA - that's an absolute max rating, a rough rule of thumb is around 10mA.

So, if you're trying to drive at 5V, and the Forward Voltage is 1.8V, with a Forward current of 10mA (0.01A), that's (5.0-1.8)/0.01 = 320 Ohms, nearest easy found value is 330 Ohms. If you want to drive at 12V, then (12.0-1.8)/0.01 = 1020 Ohms, nearest easy value = 1000 Ohms (1k).

Whichever resister value you calculate, you place the resistor in series with the LED then drive that from the DC supply.

Note, its generally considered unhealthy to reverse bias an LED - they go pop at quite a low reverse voltage. Even if they don't pop, then can be significantly degraded.

Amazon sell reflective opto-couplers - there's generally not a huge difference in the 4-pin devices (2 pins for the LED, 2 pins generally for a photo transistor). They should be pretty much interchangeable.

**John11668** · 07-11-2020

Originally Posted by Doddy

John - firstly, these are usually infra-red, so it may well have been illuminated even if you couldn't see it (hint - you can often get a mobile phone camera live-view to witness IR LEDs).

Reverse voltage?, yup, a good way to fry an LED.

The good thing is these are generally fairly standard devices, although pin-outs may vary. And drive voltages?, can be pretty much whatever you need. I'll assume you've not hit this before otherwise you'd not be asking.. Take the supply voltage, and subtract the forward voltage drop of the LED. Then divide that by your chosen forward current. That gives the value of a resistor to place in series with the LED for it to operate at that voltage. That Datasheet indicated a max forward current of 40mA - that's an absolute max rating, a rough rule of thumb is around 10mA.

So, if you're trying to drive at 5V, and the Forward Voltage is 1.8V, with a Forward current of 10mA (0.01A), that's (5.0-1.8)/0.01 = 320 Ohms, nearest easy found value is 330 Ohms. If you want to drive at 12V, then (12.0-1.8)/0.01 = 1020 Ohms, nearest easy value = 1000 Ohms (1k).

Whichever resister value you calculate, you place the resistor in series with the LED then drive that from the DC supply.

Note, its generally considered unhealthy to reverse bias an LED - they go pop at quite a low reverse voltage. Even if they don't pop, then can be significantly degraded.

Amazon sell reflective opto-couplers - there's generally not a huge difference in the 4-pin devices (2 pins for the LED, 2 pins generally for a photo transistor). They should be pretty much interchangeable.

Hi again folks
Have replaced the opto switches but i am struggling to follow the calcs above
Taking figures from page 5 of the datasheet Forward voltage is 1.7 v max with a forward current of 20mA, so with two lamps in series we have a forward voltage of 3.4.
Not sure how I choose the forward current but 20mA is the figure given in the conditions column so will go with that.

So cautiously driving with a 5 v supply 5- (2x1.7) = 1.6V and at 20 mA I calculate a resistor of 80 ohms and I dont have one.
And I still cant quite understand why Boxford were driving the same rig with a 10v output and no apparent resistor , so with tongue firmly in the cheek and having a couple of spare opto switches my inexperienced mind thinks why not give it a shot without resistor anyway.

So I wired to plus 5 v and brought the single pulse (blue wire) back to pin 12 , set this up in Mach 3 I am not understanding the other settings I see in Mach.
I get figures flashing up for true spindle speed as I switch on with say S500 but these figures die away to zero as spindle runs up.

I am bewilderd by the range of settings I may need to address so if any one can guide me I would appreciate.
I presume that spindle pulleys just selects a speed range so I think I am OK with that
But Ports and pins , spindle setup , spindle motor , motor outputs , PID settings have lost me, even before I get into Encoder settings

**John11668** · 07-11-2020

Not seeing any illumination on pin 12 as I rotate the disc past the single slot

**depronman** · 07-11-2020

Originally Posted by John11668

Not seeing any illumination on pin 12 as I rotate the disc past the single slot

I suspect with no resistor you have blown the new optical sensors
Take the pin 12 and touch it to ground. See if this triggers the pin in mach3
If it does then you have likely popped the new sensor

Paul

Sent from my iPhone using Tapatalk

**John11668** · 07-11-2020

Are there optical switches with a better voltage tolerance ?

**John11668** · 07-11-2020

Am currently trying to set up a profile in Linux cnc .
Would that be an easier to place to start .

**John11668** · 08-11-2020

Originally Posted by depronman

I suspect with no resistor you have blown the new optical sensors
Take the pin 12 and touch it to ground. See if this triggers the pin in mach3
If it does then you have likely popped the new sensor

Paul

Sent from my iPhone using Tapatalk

Have tried that and the yellow light goes out so sounds like I am stuck until I get some resistors .
Will look out for my mail early in the week.

Had a look on RSwww and literally pence each but with £4.95 postage

**depronman** · 08-11-2020

so at least you have proven the wiring is correct and the setup in Mach3 is also correct

just need the resistors and fit a new pair of optical sensors and you should be good to go

Paul

**Kitwn** · 09-11-2020

Originally Posted by John11668

Have tried that and the yellow light goes out so sounds like I am stuck until I get some resistors .
Will look out for my mail early in the week.

Had a look on RSwww and literally pence each but with £4.95 postage

That's interesting, I must have been given a business account (which has free postage for all orders) for some reason without realising it. I've been a customer for donkeys years and have never been charged postage.

**depronman** · 09-11-2020

Originally Posted by Kitwn

That's interesting, I must have been given a business account (which has free postage for all orders) for some reason without realising it. I've been a customer for donkeys years and have never been charged postage.

I think it depends where you live. In the UK postage is normally charged unless you order is over a certain amount at which point postage becomes free
I have a deal through work where by I get free postage and on most thinks a little off the price

I normally use CPC as they are local and if I need it quickly I can collect at their counter I find that I normally need something immediately so this works for me

Paul

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