Using WSP80 or WP80 Soldering Irons with Pace Soldering Stations - Page 1
Forum section: electronics / projects

author: Emrtech
author_rank: Contributor
timestamp: December 29, 2019, 10:41:20 pm
content: Both the Pace and Weller WD Series Soldering Stations for the WP80 and related soldering irons utilize RTD type temperature sensors in their heaters. The thought occured to me, I wonder if my SensaTemp stations could operate the irons correctly with an adaptation. The only electrical difference between Pace PS-90 and the WSP80 is the RTD resistance and connector pinout. Pace stations such as the SensaTemp or Sodrtek series, the ST-25 and related all have 80W rating and are well suited to piwer the Weller soldering iron, albeit the rated transformer voltage is only 21V and the WP80 won't be run at rated power. But the difference is quite neglible.I acquired recently a brand new WP80 soldering iron in a local store for a good price. I wanted to build my own station. Both irons fit inside the same station receptacle. All that is needed, is to amplifiy the PT20 by a factor 5 or modify the station electronics. I opted to build an external opamp adapter to avoid to have to modify the station. Prototyping the circuit with an LM324 and a feedback of 10K/39+1K and a 1K pullup to 5V proved that the soldering iron could be operated this way. It is a good thing to connect a 470 Ohm resistor from the opamp output to ground in order to help the output stage to sink enough current to overcome the 5mA PT excitation current coming from the station input circuit. Without it, the internal current pulls up the opamp to about 0.925V and that means, the lowest temperature that can be used this way is about 200 Degrees C. With the 470 Ohm output load resistor it works all the way down.Checking the calibration with an FG-100 reveals an error of +3 Degrees at 200C, +24 Degrees at 300C and +1 Degree at 400C. This is without any calibration or tweaking of components. For the breadboard I used ordinary 5% resistors.Update: After adjustment of offset and gain errors the dial error is now anywhere under +/-2 Degrees C under steady-state conditions. The control loop appears to be somewhat underdamped and oscillates slowly somewhat a few times before settling down. I need to compare this behaviour with a regular Pace iron. The increased loop gain might be responsible for this - need to investigate it.Anyways, I hope this might inspire you to try out this approach as well.I am not sure yet how I will make this adaptation permanent. I would like to maintain usability with Pace SensaTemp irons I have already. I might add the circuit and changeover switching inside and install an AMP connector on the back, or build it onto a small in-line electronic enclosure or inside a receptacle housing. The regular SensaTemp station have an extra pin that is unused ( normally reserved for MBT station vacuum control. The 8V from the station could be connected to this pin to power the adapter as well. The inline Adapter option actually appeals to me. The opamp circuit could fit nicely inside between the receptacle for the WP80 and a plug if built in SMD technology.I will present my permanent solution at some point in time if you are interested. The experiment has clearly proven the viability of such an enhancement.The WP80 behaves very nicely and has good power. Heating time from room temperature to 350 Degrees is 18s. The overload, the WP80 is technically causing to the transformer and TRIAC, seems acceptable. The station stays almost at room temperature even after one hour of soldering. It can't be too excessive due to the short duty cycle. Perhaps, when so, during massive ground plane soldering it may become a problem. Time will tell.