dual voltage  (glue gun ) - Page 1
Forum section: electronics / beginners

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 04, 2017, 05:44:48 pm
content: Hi,I have an hair drier that seems to work on 120-240 volts because of a SL-123-23 sliding switch and a glue gun (NYLEO mosel NL-308) having the same possibility kind of 'automatically'.Is there a tutor on this subject. I did not found one on utube.Thanks for your attention.JPD

author: frozenfrogz
author_rank: Frequent Contributor
timestamp: April 04, 2017, 06:21:48 pm
content: Your hair dryer and glue gun are quite simple applications that are most likely designed in a cost-effective way. It is quite possible that the hair dryer just consists of a universal heating element, a universal motor a switch and a resistor to select between two power modes and a self resetting thermo fuse.Another way is probably a diode bridge rectifier and a handful of parts asdescribed in this article. This would incorporate a DC heater and a dc motor obviously.There are other options however, that are more sophisticated and thus more expensive for more demanding tasks, like the switching power regulators.This thread on a glue gun teardownmight be interesting for you

author: Gyro
author_rank: Super Contributor
timestamp: April 04, 2017, 07:11:09 pm
content: The PTC element in the glue gun would certainly give some degree of self regulation but I'd be surprised if you didn't get some degree of 'hot' and 'rather hotter'.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 04, 2017, 09:15:30 pm
content: I don't have a problem. I want to know how it work. I opened the gun and there is a chip with an inductance and many sot 23 components.But I don't understand.And you? ;o)

author: Seekonk
author_rank: Super Contributor
timestamp: April 04, 2017, 09:56:56 pm
content: Usually all they do is put a diode in series with 120V heating element for higher voltage. An actual circuit seems like overkill.

author: Kilrah
author_rank: Unknown
timestamp: April 04, 2017, 10:15:41 pm
content: Quote from: J4e8a16n on April 04, 2017, 09:15:30 pmPost photos if you opened it...

author: Zero999
author_rank: Super Contributor
timestamp: April 04, 2017, 10:29:00 pm
content: Quote from: Gyro on April 04, 2017, 07:11:09 pmI doubt it's that simple. there's a temperature control dial, yet a PTC heating element would have a fixed temperature.I wonder if it heats up four times as fast on a 240V supply than a 120V supply?

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 04, 2017, 11:20:49 pm
content: Quote from: frozenfrogz on April 04, 2017, 06:21:48 pmIdon'mind the heater or the glue.i just want to know how to make a switch between 120-240 volts.

author: Brumby
author_rank: Unknown
timestamp: April 05, 2017, 12:41:18 am
content: It very much depends on what sort of equipment you will be using such a switch.

author: KL27x
author_rank: Super Contributor
timestamp: April 05, 2017, 05:56:39 am
content: QuoteI would guess so. And that it also gets hotter on 240V. It doesn't matter, so long as the range of adjustment is large enough for it to function on either supply. On 240, you would just find the useful range to be more towards the lower end.I have the same glue gun, and it seems to work as advertised. You can dial it up or down. I never gave it much thought, but my first guess is perhaps there's a triac in there? And the potentiometer scales the gate voltage? This is one of the most common ways to dial back AC mains for a resistive load.A triac can be used as a switch between 110/240 by connecting a physical switch to select between two resistor ladders. But it will only work for resistive loads. It regulates the amount of on-duty by chopping the waveform of the AC. Not all circuits will be happy with this. Full disclosure, I have never designed a circuit with a triac, so I could be wrong. I think it turns off automatically when the voltage crosses zero. And then it won't turn on again, until the voltage on the gate gets to a certain minimum. So by changing the scaling of voltage on the gate, you get it to turn back on sooner or later to change the power that is passed. So maybe I'm wrong, but I think you want a logrithmic pot if you want the action to be fairly linear.Sidenote: this is the best glue gun I have ever used for prototyping/reworking pcb's. Being able to dial back the temp (power, to be more accurate) for low duty cycle, low volume work keeps the glue from burning. My $100.00 glue gun lasted a month at this kind of work before burning out (and burning ME way too many times). In the past I have often added a rectifying diode and a switch to a glue gun to make it suitable for "on all day, but used very little" kind of work, but this gun ups the ante and was like $15.00, tops, IIRC.

author: Codebird
author_rank: Regular Contributor
timestamp: April 05, 2017, 06:09:50 am
content: There are many ways to go about this.The cheapest, nastiest way is a diode: On 230V, put a diode in series with the heater so only half the cycle is used. On 110V, the switch bypasses the diode. It works. But somewhere, an electrician is crying.That little temperature adjust dial is probably a chopper of some form - a circuit which enables power to the element at the zero-transition, and turns it off again after a time inversely dependent upon the dial.If it's a really high-quality glue gun, it might even incorporate active feedback - a temperature sensor on the hot end and a comparator, so the element is turned off once it reaches temperature. That way it will remain at a very constant temperature regardless of how fast you are squeezing glue out, plus it can be made to work over a wide input voltage range. But this raises the cost considerably, so you won't find it on the cheap ones.

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 05, 2017, 09:39:13 am
content: Thanks to all of you that's very instructive.

author: bktemp
author_rank: Super Contributor
timestamp: April 05, 2017, 09:57:06 am
content: Quote from: Codebird on April 05, 2017, 06:09:50 amDoubling the voltage quadruples the power. Adding a diode halves the power, so you still end up with double the power. But it probably doesn't care because of the self regulating PTC heating element generating a constant temperature.In this case there is probably a temperature sensor and a closed loop regulator, because open loop probably doesn't work very well in this case, because of the high thermal capacity.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2017, 10:30:40 am
content: Quote from: bktemp on April 05, 2017, 09:57:06 amBut in this case there's no voltage selection switch!

author: J4e8a16n
author_rank: Regular Contributor
timestamp: April 05, 2017, 10:45:17 am
content: https://www.dropbox.com/sh/5fg8rwbs56xt0lk/AAA-Sy_r6Bi72yqWPoJlP2Mba?dl=0

author: jeroen79
author_rank: Frequent Contributor
timestamp: April 05, 2017, 11:13:46 am
content: There is a part marked SCR on it.It looks like a basic dimmer.

author: bktemp
author_rank: Super Contributor
timestamp: April 05, 2017, 11:28:38 am
content: I would say it is more than a simpel dimmer, because there are some small wires K1/2 for maybe a sensor and a LM358 opamp. So it probably uses a closed loop temperature control. Therefore the supply voltage doesn't care much, it just heats up much quicker at 240V than at 100V.A basic dimmer circuit requires 2 resistors, 1 capacitor (forming an adjustable RC time delay) and a diac for triggering the triac.

author: Zero999
author_rank: Super Contributor
timestamp: April 05, 2017, 05:37:40 pm
content: Quote from: bktemp on April 05, 2017, 11:28:38 amLike this:http://www.next.gr/circuits/Full-wave-Phase-Control-Using-Lower-Voltage-DIAC-l54703.html