connect LED to hotend

Weedz

connect LED to hotend
August 15, 2012 10:15AM

Registered: 12 years ago
Posts: 120

Small question

Is it possible to hook up a LED to the hotend power resistor. That way i could see if its on or off.
the hotend power risistor is on or off powered right....

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rhmorrison

Re: connect LED to hotend
August 15, 2012 10:30AM

Registered: 15 years ago
Posts: 3,742

This is how it is done on the old Gen3 Extruder Controller board:

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

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Weedz

Re: connect LED to hotend
August 15, 2012 10:36AM

Registered: 12 years ago
Posts: 120

exactly just putting a 1k resistor and a LEd in parallel to the heaterresistor

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nophead

Re: connect LED to hotend
August 15, 2012 12:00PM

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Registered: 17 years ago
Posts: 7,881

The heater is PWMed, not just on off, so the LED will vary in brightness as well.

[www.hydraraptor.blogspot.com]

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Lodorenos

Re: connect LED to hotend
August 15, 2012 01:57PM

Registered: 12 years ago
Posts: 83

I assume this can be implemented on any current electronics board?

--

Charles S.
Software Engineer
Prusa Mendel I2, RAMPS 1.4, Marlin 1.0 R2, Pronterface, Slic3r

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nophead

Re: connect LED to hotend
August 15, 2012 02:30PM

Admin
Registered: 17 years ago
Posts: 7,881

Yes, just make sure the LED is the right way round.

[www.hydraraptor.blogspot.com]

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glyn

Re: connect LED to hotend
August 15, 2012 04:15PM

Registered: 12 years ago
Posts: 82

2z5q32c.jpg

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nophead

Re: connect LED to hotend
August 15, 2012 04:30PM

Admin
Registered: 17 years ago
Posts: 7,881

What sort of bed is the other MOSFET driving? In general you need to use all four pins and even then the connector may burn out.

[www.hydraraptor.blogspot.com]

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Lodorenos

Re: connect LED to hotend
August 15, 2012 04:31PM

Registered: 12 years ago
Posts: 83

Wouldn't that only have effect if you turn on a "second" extruder in your firmware?
Also, are there any specifications for the LED or does it not matter?

glyn Wrote:
-------------------------------------------------------
>

2z5q32c.jpg

Edited 2 time(s). Last edit at 08/15/2012 04:33PM by Lodorenos.

--

Charles S.
Software Engineer
Prusa Mendel I2, RAMPS 1.4, Marlin 1.0 R2, Pronterface, Slic3r

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Weedz

Re: connect LED to hotend
August 16, 2012 03:24AM

Registered: 12 years ago
Posts: 120

ah ok so it is PWM i assumed it was on of just like my heatbed.
If i put a 1k resistor infront of the LED would it then be bright enough?. if i calculate the resistor needs it would be around 420Ohms if a assume that the LED takes 1.5V and 25 mA

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nophead

Re: connect LED to hotend
August 16, 2012 03:51AM

Admin
Registered: 17 years ago
Posts: 7,881

10mA is plenty of current to be able to see it and will work with any small LED. 25mA pushes it close to absolute max for some LEDs.

[www.hydraraptor.blogspot.com]

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Weedz

Re: connect LED to hotend
August 16, 2012 04:25AM

Registered: 12 years ago
Posts: 120

ok and same would count for heatbed right. I have a MK2 heatbed but i have no room for the LED on the board itself. I have the heatbed connected to a realycircuit and i thinking of powering it from that.

i think i had some LED laying around with 35mA max but il go for 1k Res just to be on the safe side, if it will glow enough for noticing

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glyn

Re: connect LED to hotend
August 16, 2012 09:17AM

Registered: 12 years ago
Posts: 82

Quote
Lodorenos
Wouldn't that only have effect if you turn on a "second" extruder in your firmware?
Also, are there any specifications for the LED or does it not matter?

That is the main power to the extruder heater... works for me.

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Lodorenos

Re: connect LED to hotend
August 29, 2012 07:40AM

Registered: 12 years ago
Posts: 83

glyn Wrote:
-------------------------------------------------------
> That is the main power to the extruder heater...
> works for me.

I didn't see the two wires going to your hotend at first, it looked like the LED and resistor were the only connected components.

--

Charles S.
Software Engineer
Prusa Mendel I2, RAMPS 1.4, Marlin 1.0 R2, Pronterface, Slic3r

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xiando

Re: connect LED to hotend
August 29, 2012 08:49AM

Registered: 12 years ago
Posts: 477

Calculate the value based on the heater voltage supply.

R_Led = (Vs-V_f)/I_f,

where V_s is the supply voltage (steady state), V_f is the forward voltage specified for the LED in its data sheet, and I_f is the correpsonding forward current for the LED at that V_f

That it fluctuates in brightness according to the duty cycle can be looked at as a positive through the right eyes. That the LED doesn't fail if the duty cycle goes to 100% is also a positive as well winking smiley

Edited 2 time(s). Last edit at 08/29/2012 09:32AM by xiando.

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Weedz

Re: connect LED to hotend
August 31, 2012 07:27PM

Registered: 12 years ago
Posts: 120

i probably try this weekend to hook it up....
Ill add some picures when ready

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