Hakko A1321 heater only 50W @ ~3 Ohms and 24V?! - Page 1
Forum section: electronics / beginners

author: ghost_dog
author_rank: Newbie
timestamp: June 15, 2024, 12:41:41 pm
content: Hey, guys.New guy here and not a noob, but I'm placing the thread in the 'beginners' section because it's seemingly simple (OTOH, there is very little official info, so, it's not that simple (also, I've read more than a few threads, seen more than a few vids, but the Hakko A1321 heating element still has me puzzled, TBH)).Here's the thing ....The A1322 heating element is ok in terms of 'math': output declared as 50W @ 24V and ~12Ohms (24V/12Ohms = 2A => 24V * 2A = 48W).The A3121, though ........ it's supposed to be 50W as well, operating at 24V but, the resistance of the heating element is around 3-3.5 Ohms (which should equate to current draw of around 8A, which in turn should equate to power output of around 190W (not 50W)).To use genZ vocabulary, my brain isn't braining on this one.What am I missing here?!Cheers!

author: jonpaul
author_rank: Super Contributor
timestamp: June 15, 2024, 01:07:45 pm
content: Heaters use Nichrome wire.All metals have atempco of R vs T.Generally increase in R with T.Power of irons may be constant V or I and can be PWM or otherwoise regulated.Easy way to test is NOT at the tip V, but mains power IN with a mains wattmeter.Jon

author: wraper
author_rank: Unknown
timestamp: June 15, 2024, 01:08:00 pm
content: Are you sure you're not measuring thermocouple resistance? IIRC one has a resistive sensor, another has a thermocouple.

author: wraper
author_rank: Unknown
timestamp: June 15, 2024, 01:09:46 pm
content: Quote from: jonpaul on June 15, 2024, 01:07:45 pmThese do not (if they are original Hakko).

author: ghost_dog
author_rank: Newbie
timestamp: June 15, 2024, 01:21:02 pm
content: Quote from: wraper on June 15, 2024, 01:08:00 pmI have a knockoff A1321 heater, but it's one of the decent ones, and the measurements are pretty much spot on: heater - 3.5Ohms; sensor - 43Ohms.I'm thinking along the lines of: somes sort of PWM is involved (which can 'save' the heater, but I can't see the PSU not drawing ~8A in short bursts).

author: ghost_dog
author_rank: Newbie
timestamp: June 15, 2024, 02:19:18 pm
content: Quote from: jonpaul on June 15, 2024, 01:07:45 pmI have no way of testing the power draw at the mains ATM and it's a well known design, so hopefully someone will chime in.

author: magic
author_rank: Super Contributor
timestamp: June 15, 2024, 03:06:14 pm
content: A1322 and A1323 use nichrome wire which behaves more or less as you expect.A1321 is a ceramic heater with significant positive thermal coefficient. IOW, resistance increases a lot when it heats up. AFAIK it's the same for the genuine Hakko heater and Chinese knockoffs. It's annoying because these heaters may trip PSU overcurrent protection when cold. OTOH, I suppose they heat up faster if the PSU can supply the extra power.

author: IanB
author_rank: Super Contributor
timestamp: June 15, 2024, 03:18:22 pm
content: Quote from: ghost_dog on June 15, 2024, 12:41:41 pmIt's similar to a car. The cruising power at normal speed is much less than the power needed to accelerate from a standstill.An iron needs to get up to temperature quickly when you switch it on, and it needs to have rapid thermal recovery when you use it. So it needs to have an intermittent power much greater than the average continuous power. The iron will have some control and regulation to keep the tip temperature on target. This may be inherent self-regulation due to the ceramic nature of the heater, and it may be external regulation done by electronics.You will likely find that that maximum average power available from the base unit is about 50 W. That does not necessarily mean the maximum instantaneous power available at the iron is also 50 W.

author: ghost_dog
author_rank: Newbie
timestamp: June 15, 2024, 03:49:32 pm
content: I get what you guys are saying.I am curious, though, about what (really) happens before the heater reaches 10+Ohms (if it does indeed reach that resistance), because, even though the heater reaches the high temps rather quickly from a 'human' perspective, it doesn't reach them in a couple of AC cycles or so.How is the transitional period 'handled' (because there is a potential for the transformer to be 'exposed' to power draw 4x the size of nominal power draw).P.S.Even though it's not the same handle/heater, this video ........ actually corresponds really well with what can be expected of the A1321 heater (as far as I can see, the current limiter kicks in, and since there is no 'PWM trcikrery' involved, current draw is pretty high (higher than 2A anyway)).TLDR:- do we know for sure that the resistance of the heating element (not the PTC), rises with temperature (i.e. 'significantly' rises with temperature)- if the resistance stays roughly the same, how is the (rather long) transitional period handledBasically ('for now'), seems like it's up to the PSU to handle the initial 10-15 seconds of the circuit drawing 7+ Amps.Edit:- More importantly, if the resistance doesn't rise significantly with temperature, what's to stop anyone from running the heater @9V (about 2-3A of current draw, nice and safe ....)

author: IanB
author_rank: Super Contributor
timestamp: June 15, 2024, 04:28:14 pm
content: Quote from: ghost_dog on June 15, 2024, 03:49:32 pmA normal magnetic transformer is quite capable of short term loads much greater than its nominal rating. All that happens is that the transformer starts to heat up. But if the load is removed before it gets too hot, the transformer will just cool down again and be fine.This is not the case with electronic supplies such as switched-mode converters. These can't usually go above their rated output.It is of interest that my Hakko soldering station has a real transformer inside it instead of an SMPS.

author: ghost_dog
author_rank: Newbie
timestamp: June 15, 2024, 04:35:49 pm
content: Quote from: IanB on June 15, 2024, 04:28:14 pmYes, that makes sense.Hakko stations have decent transformers (pretty 'beefy', as far as I've seen), and the knockoff stations have 'questionable' transformers (sometimes the're decent as well).Hakko stations have a 'transitional period' (as far as we've established so far), and the knockoff stations (predominantly with thermocouple type sensors and 10+Ohms heaters), do not have a noticeable 10+ seconds power surge at the beginning.

author: mariush
author_rank: Super Contributor
timestamp: June 15, 2024, 04:43:45 pm
content: They use AC voltage on the heater element, so it's not a constant high voltage... they use a triac to turn on and off the element. there's an optocoupler with zero crossing detection that turns on and off the triac as close to the 0v threshold as possible.Here's a falstad simulation :https://tinyurl.com/2av3xpxjhover mouse on the scope view to see voltage and power on heater...

author: floobydust
author_rank: Super Contributor
timestamp: June 15, 2024, 05:53:35 pm
content: More info on A1321 and the fakes:https://www.eevblog.com/forum/reviews/genuine-vs-fake-hakko-936-ceramic-heater-a1321/25/Mains freq. power transformer is more reliable, no EMI dangers, weighs a lot more, and can take overload when undersized.A soldering iron's duty cycle is low, they don't run at 100% heat for very long. Overloading an SMPS doesn't work well compared to a mains freq. power transformer.I looked closely at resistance of a Hakko A1313 (470B 24VAC) heater. There, the controller senses resistance (current) to ascertain temperature. No temp sensor is used. It seems to be a specialty wire (from the day before non-linearities could be compensated for in MCU firmware). About 2.8Ω cold 23°C and 8.36Ω at 425°C. Hakko later abandoned that approach and added the temp sensor.

author: langwadt
author_rank: Super Contributor
timestamp: June 15, 2024, 06:20:34 pm
content: Quote from: IanB on June 15, 2024, 04:28:14 pmeons ago when I was in school I build a temperature controlled soldering iron, it also used a real transformer. The heater was powered with rectified AC, the temperature was measured measuring the heating element resistance in the zero crossings

author: ghost_dog
author_rank: Newbie
timestamp: June 15, 2024, 06:23:21 pm
content: Quote from: floobydust on June 15, 2024, 05:53:35 pmI've read that "genuine vs fake A1321's" thread, and it's definitely a good read (but it doesn't really answer the questions from the OP).Quote from: floobydust on June 15, 2024, 05:53:35 pmWell, they do for some time, when you turn them on (i.e. long enough for overheating/burn-out problems to appear if the transformer is 'weak').And we never really established (in this thread), what goes on when you turn on the (936 type) soldering station.Does the resistance increase with temp (or does it stay the same)? If the resistance does increase - how quickly does it increase and by how much?!As far as I can tell, so far we've established (but, not in certain terms), that the proper operation of a "936" style soldering station with the A1321 heating element, depends on the transformers ability to withstand the initial inrush of current (which is several times higher than the average operating current once the heating element reaches the usual 250+ deg. Celsius temperatures).Other than that, in the meantime I've checked out the Arduino code for one of the most well known online DIY projects ........ and apparently, there is a variable named "pwm", but it is (as far as I can tell), used only in a "ON-OFF" capacity.