Introduction: Power Supply for 3D Printer.
Power supply is the Heart of our Electronic. But unfortunately Most of our 3D printer kits does not come with an optimised one. Well It's our job to fit our requirements.
So generally a single Power supply is provided to our kit which is not so good or say optimistic.
Here I will show you how to make a dual Power Setup which will be more safe to operate and will be providing redundancy.
A 24 Volt SMPS.
An ATX power supply.
An Opto Isolated MOSFET Board.
Wires , 10 K resistance, Soldering arrangements. 120m Fan
Step 1: Separation Prevails Redundancy
The concept of separate Power supply not new. In electrical installations Control supply is always isolated from Power supply.
The reason is very simple but important.
Any deviation in Control Voltage due to Power circuit disturbance may hamper Safety and can cause undesirable result.
I had seen an phenomenon of ghosting in Prints and some typical sound of the Steppers when using DRV8825 during the PWM cyscles of Heaters.
What was happening was that during the Bed heating, the Load on SMPS is increased heavily and the voltage is getting lowered. Having a common supply to control circuit and motors the motors were acting cranky since this fluctuations are more prominent during the PID control of the heater.
So, A separate source for the Bed heater , the most power hungry component of the system can save our Day.
There is another safety or reliability aspect. Say due to some fault the Bed wires got short circuited, the SMPS does not have a short circuit protection due to low cost manufacturing regulations, You will loose the SMPS, the ongoing print and can be a risk of Fire .
Separation will result in fault separation. Only Bed Heating SMPS will get faulty.
Step 2: The Plan
Here we will be using an ATX power supply used for Computer. It have an inherent Auto shutdown on fault feature and it's pretty cheap. So using it for the bed Heating wil help our print to continue without bed Heating. The 24 Volt SMPS will be used for Control and Extrusion Heater 40 watt in my case .
A step up converter will be in between the ATX power and Bed so as to boost the heating Time by increasing the voltage to 15 Volts. The stepup conversion is optional but can be power limiter by its rating. Mine is 200 watt. A Opto isolated MOSFET will be used for switching. PWM from Main board will be feed to the board via 10 K resistance.
Step 3: Final Assembly.
The Pictures said it all.
Assembled in a Wooden Switch Board cavity.
Not too clean installation but is doing it's excellent job. 120 MM PC fan is blowing adequate amount of air with low noise. Best Part is the fire and electrical shock Hazard Unit is now separated.
Here is a video in operation.....
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Step 4: Future Scope
Since the Bed is a Resistive Load and I have a UPS transformer Lying around, Inspire of using a ATX SMPS I'd using Triac and Custom make Opto Isolator by using LDR, a cheap solution can be made.
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