DIY Weller 5 pin controller? - Page 1
Forum section: electronics / general

author: JonnyM
author_rank: Contributor
timestamp: November 02, 2016, 06:39:54 pm
content: Hi! I'm new to this forum but I'm a longtime EEVblog fan.Today I found this brand new Weller LR-21 soldering iron in the dumpsterhttp://imgur.com/a/jhbKjI'm using a Weller TPC-S at the moment but I only have 700 Fahrenheit tips for itSo this 5 pin iron would be perfect!Now i just need a controller for it. Here's a pinout of the 5 pin connector.http://imgur.com/a/G0gU5I confirmed that it's working just by applying 24v directly to the 12 ohm heater pins and it got hot in 20 sec, the thermistor changed from 21ohms to around 40ohms.Would those hakko 936 clone or t12 controllers work with this iron or do I have to make something myself? I have a lambda 24v power supply, an arduino and some mosfets from my 3d printer builds laying around.

author: Gyro
author_rank: Super Contributor
timestamp: November 02, 2016, 07:11:19 pm
content: Hi, and welcome,I suspect that you would have reasonable success with one of the ebay controller kits. I believe the Hakko etc sensors are PTC, so at least your resistance is going in the right direction.The only issue might be temperature calibration. I doubt if the source for the firmware for those controllers is available so you might be reduced to adding series / parallel resistors to get within their calibration range, that doesn't sound impossible though.Maybe a little internet research to see if you can find a T12 temperature sensor curve....

author: 2N3055
author_rank: Super Contributor
timestamp: November 02, 2016, 07:37:48 pm
content: google is your friend.... search for "weller controller schematic" gives several designs that will help you...

author: JonnyM
author_rank: Contributor
timestamp: November 03, 2016, 04:44:30 pm
content: Quote from: Gyro on November 02, 2016, 07:11:19 pmMy weller goes from 21-45 ohms while the hakko goes from 70-120 ohms. The resistance increases abit more per degree C on the hakko. I guess I could put a 50ohm resistor in series and just make a new temperature scale if I order the hakko controller.

author: JonnyM
author_rank: Contributor
timestamp: November 03, 2016, 04:47:36 pm
content: Quote from: 2N3055 on November 02, 2016, 07:37:48 pmI'm not sure if I'm capable of making the pcb for the stock controller yet. But thanks for your suggestion, maybe I have to watch some Kicad tutorials on youtube

author: rbm
author_rank: Regular Contributor
timestamp: November 03, 2016, 11:52:16 pm
content: This design is for the DSX80 but might work for your LR-21.http://silicium31.chez.com/Electronique/DS80/DS80.htm

author: P90
author_rank: Frequent Contributor
timestamp: November 04, 2016, 12:03:25 am
content: Quote from: JonnyM on November 03, 2016, 04:44:30 pmA hakko clone handle, complete with tip and heater costs less than a 50ohm 50w resistor...

author: JonnyM
author_rank: Contributor
timestamp: November 04, 2016, 02:31:46 pm
content: Quote from: P90 on November 04, 2016, 12:03:25 amI'm just going to put the resistor in series with the PTC sensor not the heating element.

author: P90
author_rank: Frequent Contributor
timestamp: November 04, 2016, 03:17:08 pm
content: Ooops, what was I thinking...Nevertheless... lol...

author: JonnyM
author_rank: Contributor
timestamp: November 04, 2016, 05:14:30 pm
content: I ordered the $3 hakko 936 controller. I'll use a 50ohm resistor in series with the sensor and maybe add a resistor to one side of the pot to limit the max temperature. I'll have to tinker when I receive the controller unit. My old weller WTPCs transformer should work great. Thanks for your suggestions!

author: Gyro
author_rank: Super Contributor
timestamp: November 04, 2016, 09:28:24 pm
content: QuoteI'd try to keep your WTPC setup intact. Fit a SSR to take the load off the thermo switch contacts and buy it a 600'F tip - it will love you forever.Edit: I just wanted to place this link here so it can be found in future. It might be of use to other Weller TCP owners...http://www.vintage-radio.net/forum/showthread.php?t=67035

author: Ton
author_rank: Regular Contributor
timestamp: November 05, 2016, 09:44:59 am
content: Hiyou could also take inspiration from some Weller designs, here is some for the PU80 the power unit for WSP80.Very similar to the LR21 except the heating element is 80W, thermistor looks the same.First time for me to do attachments, so hope it worksBr ton

author: macboy
author_rank: Super Contributor
timestamp: November 15, 2016, 07:33:19 pm
content: I believe that Weller irons that use that 5 pin connector use a Platinum RTD as a sensor, not a plain thermistor. This means that there is a high degree of consistency from iron to iron, so you can use any iron on any base without the re-calibration necessary for a thermistor. I have a very similar iron, a FE-80 (looks identical to yours, with the addition of a fume extractor), and I use it with a base that is definitely not designed for it, but it works perfectly.I have no idea what sensor other brands use.