Thank you ic racer for this! Appreaciate the sumup!
The EST provides these basic functions to the head after it recieves an ON input from the timer:
Power and timing of the fan including a thermal switch
Regulated power to the lamp, (including low idle current when off)
Power to the shutter and timing for opening and closing
I think that is it, but I hope Gary chimes in with a more detailed description of his masterpiece!
Picture with parts named. This is 230V.
The resistor is put in series with the bulb during startup. Once in idle mode with a preheated bulb the relay is closed.
values;
-preheat voltage across bulb 15V rms max. Ramp-up preheat time ±17 seconds.
-idle 16,8V_rms
-working 117V_rms
From the picture my guess is a 240v timer input activates the relay in the middle. That signals the Arduino to start its sequence via an input on the Arduino board. Looks like 240V power goes to the ON/OFF switch from the left lower corner and splits 3 ways to the Kemo, fan relay and Meanwell power supply. From the Meanwell, there is a 5v stepdown to run the Arduino.
The Arduino, via PWM, controls the the lamp via the Kemo and the shutter via the relay board (with its 5v power from the 5v stepdown board).
Looks like the original multi-connector to the head (hidden behind the solid state relay) is used to carry the power to the head.
What I can't tell is the reason for the 22 ohm reisstor and relay ( controlling inrush current to bulb?). Though the Kemo says it is "Soft Start."
I use this resistor https://www.conrad.com/en/p/widap-160127-resistance-wire-22-packaged-100-w-1-1-pc-s-1525269.html
View attachment 384957
Please note that two things are important to understand.
-One. the whole thing is controlled by the Arduino. You will have tot understand programming language for the Arduino. The Kemo Power Control will get the necessary signals from the Adruino.
-Two. The voltage has to be measured in RMS. Do not use a ordinary volt meter.
3) The only resistor I found is a 22ohm 50W one. I am afraid that 17 Seconds might damage the resistor.
I want to use a web interface to control my enlarger.
Ohm's law applies to a resistor. If the full voltage it sees is 16V, then I = V/R = 16/22 = ca. 725mA. Furthermore, P = I2*R and this works out as 11-12W. A 50W resistor should survive, provided you offer a means for the heat to be actually dissipated. Do not assume that a 50W resistor all by itself will survive having to dissipate >10W for an extended period of time. Mind you, the lamp is part of the circuit as well, so the resistor won't drop the full 16V most of the time. As the lamp heats up, that will start to eat up some of the power.
To each their own, but the utility of this evades me, to be honest. This comes from the guy who does actually control his enlarger from an ESP32, but I never saw the purpose of trying to control it from a computer or smartphone. It's fancy, that's for sure, but I don't really see how it helps in any way to be able to do this.
The 1000W @ 120V bulb
The lamp pre-heat circuit is to promote lamp life.
P=10,23W, does that mean my 100W resistor can be on for approx. 9,8sec? Or do I misunderstand?
I purchased 1x 5V Power supply, 1x 24V Power supply
6) Do you guys see any problems in my understanding of this, to me, it seems quite simple. Control Fan, shutter and the lamp. Am I mistaken?
7) If I program in a test strip mode, I will most likely let the lamp run over the full duration and just use the shutter in between.
A 100W resistor can in theory dissipate 100W applied to it for eternity. However, I state in theory, because in practice it depends on where the heat is going. Even though the part itself is capable of dissipating 100W, that energy needs to be drained away from it. If this doesn't happen effectively, even 10W applied to a 100W rated resistor can burn it out. However, your resistor would be overrated by a significant margin and I wouldn't worry too much about running 10-15W through a 100W device for 10 seconds even if thermal design isn't very good. The main scenario you have to take into account is if the 10 second period is repeated rapidly - for instance because you somehow manage to get your Arduino/ESP32 in some kind of loop where it restarts all the time.
Keep in mind that Watts = Joules per second. So 10W during 10 seconds = 100 Joules. It takes. 4.2J to heat 1g of water by 1 degree. This gives you a bit of a feeling for what kind of magnitude you're working with. It's not all that much energy in your specific case. The metal housing of the resistor and whatever metal case it's bolted to will easily manage.
Just checking - you've verified that both of these can source the power needed? The 5V will just be for the ESP32 board and the relays, I assume. The 24V is only for the fan in the enlarger head, and/or also the shutter? What's the peak current draw on the shutter solenoid?
That'll work and is a good project to get your feet wet in microcontroller engineering. It's not too difficult, it's useful and there's a couple of manageable challenges along the way that'll enable you to learn.
One thing to consider is that you may want to keep the fan running a little longer after you've turned off the lamp. On my present enlarger light source (3-color LED) I keep the fan running 20-30 seconds after the light cuts out to help dissipate the heat generated during the exposure.
I'd just cycle as you normally would, really. You'd still be repositioning a piece of card etc., which would take at least half a second or so. Turning on the lamp from idle to full power is something like 20 milliseconds. And since it's kept hot in idle mode, I wouldn't worry too much about thermal stresses. The shutter can be used to ensure consistent exposures by skipping over the warm-up period of the lamp. Not that this warm-up period is all that much of an issue anyway. Most enlargers just turn on/off the lamp and fine prints are made with these all the tiD
What does cam mean in this context? Are the micro switches there as end stops for the motor to turn off? So that It doesn't over drive the gear and shutter mechanism? I was wondering about this anyway, was not yet able to remove the shutter mechanism from the head.The shutter is operated by a 24v motor with an analog logic circuit using a cam, micro switches and a relay. There is a gear reduction unit that drives a rotating pin/lever mechanism to open and close the shutter.
On the CLS2000 (that I have) the two fans only stay on if the head gets pretty hot due to a thermal switch.
The CLS1000 single fan always turns off after the exposure. There is no thermal circuit.
Of course if the OPs circuit is controlled by arduino programming, the fan behavior can be easily changed in the programming.
Do you by any chance have experience with displays I could use for my timer unit? I was considering an e-ink display, but the refresh rate seems odd. Especially considering a timer function that ticks down. Viewing angles and backlight would not be an issue tho. Segmented displays are also an option, maybe with a yellow backlight, since it's easy to filter towards the spectrum needed for BNW.
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