Soldering Station Thermocouple VS Heating Element Resistance Sensing - Page 1
Forum section: electronics / general

author: Dawn
author_rank: Regular Contributor
timestamp: June 02, 2012, 10:45:46 am
content: Erik's earlier post on his Blackjack rework station turned up a surprising result. The 6 pin configuration of his soldering iron turned out not to be the typical Hakko 936 style 4 wire heater & thermocouple element plus frame ground using the M900 style tips. Instead, it's a two wire, intergrated heater/tip combined running 3 to 4 times the cost of a clone tip. I'm starting to notice a trend with the newer Chinese stations arriving seem to be migrating away from the Hakko 4 wire heater design especially at wattages over 45 watts. ATTEN used the two wire(core?) elements with the standard Hakko tips, but recently has changed over to the integrated tip/elements primarily in their higher wattage stations. Aoyue has done the same on their newer, 2900 stations and the updated 27xx silver rework workstations with 70W irons. Kirk's CSI/Blackjack is a hybrid based on Aoyue's 27xx series. One of the features these stations are promoting is the integrated tip/element has better heat transfer.What remains is the question of which design is better. ATTEN's 201D that's been sold under every name from Radio Shack,Tenma,Harbor Freight, to Madell has been routinely excoriated for not using a thermocouple element in reviews. I really don't have any input yet to see how they compare until my clone FG-100 tip thermometer arrives.It would make sense for the companies that use a common, 6 port/interface for all their tweezers and desoldering tools that don't use a thermocouple either to use a common connector and have the utility of 3 extra connections for pump switching or reed switch sensing once the iron or device is set in the holder.Can anyone comment on which design potentially has a tighter regulation and response?

author: T4P
author_rank: Super Contributor
timestamp: June 02, 2012, 11:07:10 am
content: Of course element resistance sensing is the best, i think what they are copying now is ... the FX951 i thinkelement resistance is instant ( obviously ) provided the sense circuitry is fast enough ...Oh by the way, how do they do it ( ... i don't really know ... comparators ? Opamps ? )

author: robrenz
author_rank: Super Contributor
timestamp: June 02, 2012, 01:13:34 pm
content: According to their literature JBC uses a heating element that is also a thermocouple. So it would be 2 wire but not using resistance change with temp but actual thermocouple with a cold junction compensation in the control unit. JBC regulation/response is definately one of the tightest/fastest from what I ahve read and experienced with mine.

author: saturation
author_rank: Super Contributor
timestamp: June 02, 2012, 04:02:00 pm
content: The response and heat transfer is better if the heater/sensor/tip were all in one, so you don't have issues regarding parts fitting and integration. Also, the closer the heat sensor is to the tip, the better the feedback and thus more accurate the tip temp is, otherwise you have an 'offset' which represents a difference between the tip mass versus the mass of the base. You can compare responses above.The question becomes is it worth the extra cost of the newer tips and the station? Clearly, every step in integration is better, between these and the oldest. But, then why not the JBC heating model? or the Metcal model?I think as you move up, you have to justify the cost over productivity, so the heavier your soldering needs, the more you'd benefit from the better station. Currently, the FX888 type technology is the lowest cost that still meets IPC standards.However, as production methods improve, the maker may find out that its no longer cost effective to manufacture low cost stations, then you are forced to move up, just like with DSOs, the 25 MHz models cost almost as much as the 50 MHz, at least comparing the Rigol 1052e to other brands. But until that day comes, or parts are not available, a buyer needs to see what is the most cost effective for their level of work.

author: sparkybg
author_rank: Regular Contributor
timestamp: December 30, 2012, 03:31:49 am
content: For Hakko 70W T12/T15 tips (BJ Solderwerks BK3000+ for example) with integrated heater, the heater is also thermocouple. Temperature is measured on every mains voltage period. When mains voltage is near zero, the power to the tip is cut, and then the thermocouple voltage is amplified by a LM358 opamp and fed into an ADC. So, it seems it is more or less the same as JBC.Soon I will be able to test if JBC 245 and HAKKO T12/T15 tips give comparable voltage from the heater/thermocouple.

author: diogoc
author_rank: Contributor
timestamp: January 31, 2013, 11:14:13 am
content: Do you have already tested the T12 tips thermocouple?

author: sparkybg
author_rank: Regular Contributor
timestamp: March 01, 2013, 08:09:28 am
content: Quote from: diogoc on January 31, 2013, 11:14:13 amYes. 18-19 uV per degree. It is positively a thermocouple. I've made my own controller. Nothing form original BK3000LF electronics left in the box. Only the power transformer.Here you can take a look at it:http://dangerousprototypes.com/forum/viewtopic.php?f=56&t=2457&p=50627#p50627

author: diogoc
author_rank: Contributor
timestamp: March 01, 2013, 10:23:28 pm
content: Quote from: sparkybg on March 01, 2013, 08:09:28 amI know. I talked with you there