I use a glue gun from time to time and was getting annoyed with the cable, finding a free power socket, was always in the way, ...
So I bought a cheap battery-powered glue gun. It takes 7mm sticks instead of my old one - which takes 11mm ones.
It also takes a little less space and has a better stand. The old one is rated at 15W while the yellow toy has 8W written on its label.
No surprise in finding a standard 18650 cell in there. The glue stick feeds through a rubber o-ring. The only electronic intelligence can be found in the board at the bottom of the unit.
The bottom of the board features a standard (90 degree) micro-USB socket and three LEDs. The LED diffuser is pictured bottom-left, while the hand-soldered "ON" switch is center.
The bottom of the board has a TP4056 battery charger IC. It can supply up to 1A of charging current (and it does) and is produced by the NanJing Top Power Corp. While it looks like the same part number and provides similar functionality it is completely different than the LTC4056.
The Linear part datasheet contains an application note where the same chip is used for charging NiMH and NiCd batteries. This hack can also be performed with this chip, if the Vbat pin is set to a voltage between 2.9 and 4.2V. But nobody wants to go back in time...
The heating element has a rubber-like surround, probably to keep the stick pushing toward the front. That's all I know.
The heating current is drawn directly from the battery, so the gun can theoretically be used while charging. However, theoretically, if the battery voltage drops under 2.8V, the IC will enter trickle-charge mode (for recovery) which will render the gun useless. In this case, you want to make sure that the battery is at least halfway-charged before using it.
I haven't traced the board, but it seems the switch directly connects the heater to the battery, with a blue LED in parallel. This is why, when charging, both the red and green ones will light up.
Out of the box, battery life seems decent. The gun stayed on for more than 60 minutes, even without a full charge. Once the battery voltage gets really low, the blue LED will start getting dimmer until it eventually shuts off. The green led will light up when the unit is fully charged.
It doesn't seem like there is any low-voltage protection, so forgetting to turn off the gun will probably kill the battery.
The charger resistor (R4) is marked 1201, that's 1.2kOhms, which means the charge current is set to 1A through the PROG pin.
If deeply discharged, the battery will start charging at 100mA, after 2.8V it will switch to 1000mA.
Unfortunately I haven't taken the battery out of the plastic wrap to check the markings and I haven't measured the heating element resistance or temperature behavior. Might do that when I will get really bored.
Measured through a USB power meter, the battery takes 3.5 hours and 2000 mAh for a full charge. Some of that energy will go into heating the charger IC (0.5~1W in constant-current mode) so the battery is likely around 1800mAh.
Heating time, with a fully-charged battery, is around 5 minutes, comparable with my old 220V unit.
Anyway, if you want to purchase one through an affiliate-link, here it is: http://amzn.to/2jlg7LV. It's currently priced at 18.99€.
So I bought a cheap battery-powered glue gun. It takes 7mm sticks instead of my old one - which takes 11mm ones.
It also takes a little less space and has a better stand. The old one is rated at 15W while the yellow toy has 8W written on its label.
No surprise in finding a standard 18650 cell in there. The glue stick feeds through a rubber o-ring. The only electronic intelligence can be found in the board at the bottom of the unit.
The bottom of the board features a standard (90 degree) micro-USB socket and three LEDs. The LED diffuser is pictured bottom-left, while the hand-soldered "ON" switch is center.
The bottom of the board has a TP4056 battery charger IC. It can supply up to 1A of charging current (and it does) and is produced by the NanJing Top Power Corp. While it looks like the same part number and provides similar functionality it is completely different than the LTC4056.
The Linear part datasheet contains an application note where the same chip is used for charging NiMH and NiCd batteries. This hack can also be performed with this chip, if the Vbat pin is set to a voltage between 2.9 and 4.2V. But nobody wants to go back in time...
The heating element has a rubber-like surround, probably to keep the stick pushing toward the front. That's all I know.
The heating current is drawn directly from the battery, so the gun can theoretically be used while charging. However, theoretically, if the battery voltage drops under 2.8V, the IC will enter trickle-charge mode (for recovery) which will render the gun useless. In this case, you want to make sure that the battery is at least halfway-charged before using it.
I haven't traced the board, but it seems the switch directly connects the heater to the battery, with a blue LED in parallel. This is why, when charging, both the red and green ones will light up.
Out of the box, battery life seems decent. The gun stayed on for more than 60 minutes, even without a full charge. Once the battery voltage gets really low, the blue LED will start getting dimmer until it eventually shuts off. The green led will light up when the unit is fully charged.
It doesn't seem like there is any low-voltage protection, so forgetting to turn off the gun will probably kill the battery.
The charger resistor (R4) is marked 1201, that's 1.2kOhms, which means the charge current is set to 1A through the PROG pin.
If deeply discharged, the battery will start charging at 100mA, after 2.8V it will switch to 1000mA.
Unfortunately I haven't taken the battery out of the plastic wrap to check the markings and I haven't measured the heating element resistance or temperature behavior. Might do that when I will get really bored.
Measured through a USB power meter, the battery takes 3.5 hours and 2000 mAh for a full charge. Some of that energy will go into heating the charger IC (0.5~1W in constant-current mode) so the battery is likely around 1800mAh.
Heating time, with a fully-charged battery, is around 5 minutes, comparable with my old 220V unit.
In use, the gun works just fine, when left unused it drips only slightly. More than adequate for light uses, probably inadequate for large quantities in a short time. But that's the usual tradeoff with any 7mm glue gun.
The kickstand is a joy and the gun has a nice design detail: protrusions next to the glue stick, on which, those with large hands, can rest their thumb.
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