I always liked good quality soldering tools, even though I currently have a nice ELV 50 Watts digital soldering station, I decided to build my own soldering base station using an existing WPS80 soldering iron manufactured by Weller. After looking on the net to see others DIY projects I decided to develop a different one, with several improvements in the design.
The main criteria for the design was that the device should be very compact, since I don't like big boxes on my crowdy workbench. Therefore I selected a small enclosure available from Hammond manufacturer and designed the PCB to fit inside the box without many adaptations. As you can see in the pictures bellow the main component is the big trafo (100VA toroid 2x24V); the electronics occupies a small fraction of the available space.
The electronic circuit was designed with several aspects in mind; first it should be fairly simple for anyone to build (as few components as posisible), even if it uses SMD components. Secondly, the reduced size of the electronic circuit is mainly achieved by using a power MOSFET transistor without the need of an additional heat-sink. Most of the DIY (and comercial) soldering stations that I found on the Internet used triac + driver topology for the heater but that solution needs extra heatsink for the power triac. These solutions have an advantage however, the commonly used driver chip is an opto-triac driver (eg. MOC3041) which is simple to drive and has additional 'zero-crossing' detection logic available.
The core component of the schematic is the ATMEGA164 type AVR micro-controller specially selected for PGA circuitry it has for ADC differential channels. This important feature avoids the need of an external OPAMP used to amplify the signal from temperature sensor (PTC in Weller's case). The temp-to-voltage conversion is handled by an constant current circuit implemented with LM1117 LDO chip, this ensures great linearity of the PTC readings. The logic power supply uses an SPMS circuit LM2674 which means we can directly use power trafo outputs (24VAC with full wave rectifier and capacitive filter). Of course the SMPS does not need a heatsink either ;).
The user interface is simple enough, I purposely selected an 3xDigits LED display since it has nice contrast ratio in almost every illumination conditions. For temperature setting I selected a cheap rotary encoder which greatly simplifies the operation modes.
As you can see from the pictures the display board directly plugs into the "main board" with no additional airwires, further more the main PCB is single side routed with very few airwires.
Here is a simplified list of important components (not so commonly available) of the project
|HM-1455N1201||Aluminium enclosure box||A:120mm; B:53mm; C:103mm|
|TTS100/Z230/24-24V||2x24V toroidal trafo, 100VA, 2x2.08A, 230VAC||Breve Tufvassons, 100VA type|
|ED16112O||Rotary encoder||24 pulses/rotation, 24 dents|
|ZL263-16DG||2x8 pins connector, right angle||Used on LED display daugther board|
|BC56-12SRWA||LED display, 3 digits, common cathode||Kingbright Electronic|
|C091-3437-000||Circular connector, 7poles||AMPHENOL, 7-poles, circular connector
used for soldering iron plug, modified by
cutting a new key opening near pin 7
The equally important part of the project is the software, which implements the temperature controlling loop (PID with anti-windup) and the user interface. The output control is synchronized with the mains frequency (50Hz here in Europe), by using an "zero cross" simple circuit in order to minimize the commutation noise and associated EMC problems. The ADC reads the PTC sensor during OFF time of MOSFET PWM and the samples are massively averaged (moving average filter), this greatly increases the readings stability and accuracy.
SW4.1: eSol_Software_V4.1.zip : Corrected behaviour on eSol with the 2 buttons fitted
SW4.0: eSol_Software_V4.0.zip : Decimal dot used as heater activity indicator. OS improvements
SW3.0: eSol_Software_V3.0.zip use it for HW3.0: IC4=LM1117IMP-ADJ/NOPB, R2=47R, R3=1K12
Improved PTC range, calibrated temperature/voltage transfer curve
SW2.0: eSol_software_V2.0.zip use it for HW2.0 IC4=LM1117M-1.8/NO, R2=150R, R3=1K5
Added standby mode, display routines cleanup/optimizations
SW1.0: initial version
If you are not interested to modify/improove the software functionality you can directly flash the provided hex file into the microcontroller. Be sure that you change the following fuse bits settings:
The project results are very encouraging, the temperature is maintained in between few Celsius degree range, the heating time is very fast (comparable to Weller's soldering base stations) and the overall device size is smaller than the original equipment.
Here is a side by side comparation with Weller device:
Here is a short video of eSol running:
The software of the project is free to use even for comercial purposes, subject to the GPLv3 license.
If you have questions related to the projects don't hesitate to use the comments section bellow, we will try to answer all your support requests. For special requests or discussions you can contact us on e-mail:
1. Where I can buy such soldering station?
I don't know, I only designed it and don't intend to do manufacture business.
2. How much does it costs?
Again, I don't really know, however keep in mind that this is not a replacement for cheap commercial soldering stations, as a matter of fact I think you can buy cheaper Chinese devices available on the market. The Weller soldering iron, the big toroid trafo and the aluminium enclosure are the expensive components of such project.
3 Can this device work with cheap soldering irons from the market (Solomon, Pensol, ...)?
Not directly. Why would anyone build a not_so_cheap soldering base station to use it with low cost irons, instead of buying the cheaper Chinese soldering stations completely?
4. Can you adapt this project on my SL10 type soldering iron?
Probably yes, but currently I don't have such interest nor the available time to do it.
Since the design is open it shouldn't be so hard for anyone to modify this project according to ones needs :).
5. My trafo is only 1x24V can I use it instead of designed 2x24V one?
Yes, but with minor changes on full wave rectifier (you need an external rectifier bridge). You should also preserve the "zero cross detection" wire connected to one of the trafo outputs. From our tests the Schottky diode from zero-cross sensing circuit also needs to be replaced by a regular diode (with higher voltage drop on junction)