Heating a desolder gun with a T12 type controller [COMPLETED] - Page 1
Forum section: electronics / projects

author: enut11
author_rank: Super Contributor
timestamp: October 04, 2024, 04:19:02 am
content: I inherited most of the parts to build myself an electric vacuum desoldering station. The only thing missing was the temperature controller.Knowing almost nothing about soldering iron controllers I thought it would be OK to purchase a multi-controller believing that at least one of the options would work.Sadly, no. Error message is "No Tool".The desolder gun (Duratech TS-1386) has a 7-pin plug with separate pin pairs for heater, TC and switch. The 'T12' controller has a 5-pin socket and came with a new matching plug. I set about rewiring the 5-pin plug to the gun and this is where I started to scratch my head.The Gun has separate heater and thermocouple wires whereas the 'T12' has only one pin allocated for temperature so there must be some internal connection for the second wire (I do not own a 'T12' iron to check).Question: Is there a solution here or are the parts incompatible?enut11EDITLink to the LCD controller I purchasedhttps://www.aliexpress.com/item/1005006016472732.html?spm=a2g0o.productlist.main.61.48dcqLaEqLaEu4&algo_pvid=deada4b2-5a92-48a0-8a95-e73175b37f73&algo_exp_id=deada4b2-5a92-48a0-8a95-e73175b37f73-30&pdp_npi=4%40dis%21AUD%2143.09%2124.99%21%21%21205.00%21118.89%21%402103243417280161958117053e2b7e%2112000035337558347%21sea%21AU%21141583664%21X&curPageLogUid=OQ8jNQXsbU3X&utparam-url=scene%3Asearch%7Cquery_from%3A

author: elektryk
author_rank: Regular Contributor
timestamp: October 04, 2024, 04:48:32 am
content: It may work configured as C245, but there's a great chance that temperature coefficients will be different.

author: enut11
author_rank: Super Contributor
timestamp: October 04, 2024, 05:55:55 am
content: Thanks @elektrykI will give it a go. Do you know if the other end of the thermocouple is connected to the + or - power supply?BTW, I do not want to use the mercury switch. Is Pin1 to be left open or closed?enut11EDIT: Open mercury switch works

author: enut11
author_rank: Super Contributor
timestamp: October 04, 2024, 06:47:00 am
content: I measured the output of the gun thermocouple while heating the tip end and identified the +/- leads. I then connected the -ve end of the TC lead to the heater -ve and the controller started. That's the good news.Max temperature that I could measure at the gun tip was 137C when the controller maxed out at a 500C setting.Looks like the gun TC output is not compatible with the temperature calibration of the C245 type iron.

author: elektryk
author_rank: Regular Contributor
timestamp: October 04, 2024, 06:52:46 am
content: Does this board have calibration option?If not, you can look for an op amp on the PCB and modify the gain or add a voltage divider between the TC and the PCB.

author: enut11
author_rank: Super Contributor
timestamp: October 04, 2024, 09:42:27 am
content: As part of my understanding of how these controllers work I fitted an ammeter. I was surprised when, from a cold start, the current went up to 8A. For an 18vDC supply, this is 144 watts!The Duratech is rated for 80W so I need to look into this. Perhaps one of the other modes in this controller has a lower 'cold current' otherwise the gun might have a shorter than expected life :-(

author: elektryk
author_rank: Regular Contributor
timestamp: October 04, 2024, 11:17:46 am
content: It looks like ZD915 which is 24V 80W rated, so 18V should be also ok.Maybe heating element is non linear, does the current drop after a while?

author: enut11
author_rank: Super Contributor
timestamp: October 05, 2024, 04:17:48 am
content: Hi @elektrykYes, it turns out that all controller modes are the same - there is an inrush of 8-9A for a few seconds so this must be normal.Your idea to attenuate the gun temperature signal output worked. I reduced the TC voltage by about 2/3 (680R+270R divider inside the gun) and I now see sensible temperatures on the LCD screen which correlate fairly well with a second TC reading the gun tip temperature. This project is now done.Thank you for your input, much appreciated.enut11NOTEThere were a lot of learnings for me here. Unless you have good trouble shooting skills and the right equipment I would caution anyone from attempting this mod. Finding the correct gun temperature feedback signal was not easy as it required careful monitoring of mV while varying the temperature and trying to correlate this with the on-screen readings.Do so at you own risk but if/when you succeed, it can be very rewarding in both knowledge and equipment.