Blinking led light on heat bed

[bauf]

I've noticed that when i print stuff, the red LED on the bed keeps blinking. And today i installed 3 LED strips on each alu. And now the LED strips and the red LED on the bed blinks when running.
So i measured the 12v rail from the psu, and the voltage drops down to 11.4-11.6 when i print. I thought this psu had plenty of juice to keep things going and then some?

[RAMTechRob]

The Solid red light means the heat is on. Is that what you mean by blinking? It should turn on and off, but not blink fast.

[Brian]

The heater is controlled by a dedicated power signal that is either ON or OFF. If you use the stock configuration with stock supply, then the power that makes the heater warm up is either 12V or 0V and nothing in between. This makes the circuit very reliable and low cost.

The Red LED is connected to the same power as the heating element, so the LED is ON when the heater is ON and OFF when the Heater is OFF.

To make the heating more "precise", a software technique is used that pulses the power to the hater ON and OFF over a short time period to simulate a value that is "in between" ON and OFF. So if the printer was close to the target temperature, it might want to lower the power to the heater to 50%. Since the circuit is only capable of being ON or OFF, a 50% value would be to turn the heater ON for 50% of the time and OFF for 50% of the time. Using this pulse technique makes for very accurate control using simple circuits and software.

So the light is supposed to be blinking, as the printer adjusts the heater to values between 1% and 99% of full scale.

[teoman]

The heater is controlled by a dedicated power signal that is either ON or OFF. If you use the stock configuration with stock supply, then the power that makes the heater warm up is either 12V or 0V and nothing in between. This makes the circuit very reliable and low cost.
.

And by low cost he doesnt mean cheapo. The bed has so much thermal mass that tis is the preferred means of controlling it. This is how one would do it if designing a very expensive system. If you were heating a few nanograms or grams and you had to keep it withing 0.01 degree then you would seek alternative methods.

[bauf]

Ok,i see. Yes the red led is blinking,when it has reached the desired temperature,but the led strips dims everytime the red led blinks. But the led strips use its own yellow and black wire from the big connector. So is this normal? Quite annoying when the led strips dims constantly.

[teoman]

I do not have led strips but the rambo fan changes speed when the heaters come on. I can hear it.

[Brian]

LEDs change brightness depending on the amount of current they receive. If you are putting a resistor in series with the LED and connecting them to the yellow 12V wire, then it's quite likely that when the heater switches on, it puts a load on the 12V and can drop it by some amount. If we say it drops by 5%, then the current for the LEDs will also drop accordingly.

If you replace the series resistors with a constant current source for the LED driver, then the current will be independent of input voltage and the LEDs will have a constant brightness. You can build a simple constant current source using a few discrete parts. There are even some nice examples made from a 3 terminal linear regulator like a 7805.

You could also probably just use the 5V output or 3.3V output of your power supply to run the LEDs, but you will have to lower the series resistor(s) value(s) that are in series with the LEDs.

[Tinyhead]

I've got lights on my machine too. It's typical that they dim/flicker slightly when the bed is pulsing on and off. Just a function of the LEDs with the V-drop.

[teoman]

Add a massive capacitor.

[Eaglezsoar]

If you have a dedicated wire that goes only to the LEDs then adding a large capacitor in parallel with that wire might work but
I agree with Brian about using a constant current device that feeds the LEDs.