On 2024-01-28, John Larkin <jl@997PotHill.com> wrote:
> On Sun, 28 Jan 2024 09:14:20 -0800 (PST), "rhor...@gmail.com"
><rhorerles@gmail.com> wrote:
>
>> I want to use an EC1 rotary encoder to control a battery powered device. The EC1 sports a momentary switch, rather than an on / off switch, however, so I need to add a circuit to latch the momentary pulse. Figure 3 on this page should work: http://www.mosaic-industries.com/embedded-systems/microcontroller-projects/electronic-circuits/push-button-switch-turn-on/latching-toggle-power-switch.
>>
>> The battery will have an output boltage between 17V and 25V, and the device can use up to 10 amperes, however, so the IRF3719 dual MOSFET suggested on that page won't quite work. Instead, I am using an FQP47P06 P-channel power MOSFET as the main switch and a 2N7002 N-channel MOSFET as the gate driver for the FQP47P06. I don't know why, but it isn't working, however. When the button is pushed, if the device is off, the switch properly turns on, but when the device is already on, pushing the button does nothing. With a 22.0 Volt battery input, pushing and holding the switch brings the voltage at the gate of the 2N7002 to 19.9 Volts, which implies a drain current of about 0.2 milliamps in the 2N7002. That sounds about right.
>>
>> Looking at the scope, it takes about 150 - 200 ms for the voltage to reach this value, which also seems about right, and as expected, it takes considerably longer for the voltage at the 1uF capacitor to recover to near 0V. I am surmising the 19.9 V level experienced at the top of the cap is not high enough to shut off the FQP47P06. I wonder if the modification below would help?
>>
>>http://siliconventures.net/images/Flashlight%20Switch%20Update.PNG
>
> The circuit image is cropped but looks wrong. Spice it.
>
> It technically violates the abs-max gate voltage spec of the 2N7002,
> but it would probably survive.
>
> I recently bought a bunch of LED flashlights from Amazon. Machined and
> anodized, adjustable focus, single AA battery, three blink/intensity
> modes, really interesting light pattern. $3 each. How can they do
> that?

Perhaps they buy them on Aliexpress for $2
https://www.aliexpress.com/item/33020731608.html

Or to answer the implied question, the manufacturers are not buying
their parts from Digikey.

Stick a 14500 lithium-ion cell in there instead of the AA for increased
brightness. These are great for reading laser marking on ICs, also
inspecting drywall for flatness etc.

--
Jasen.
🇺🇦 Слава Україні

On 2024-03-03 09:16, Jasen Betts wrote:

> Perhaps they buy them on Aliexpress for $2
> https://www.aliexpress.com/item/33020731608.html
>
> Or to answer the implied question, the manufacturers are not buying
> their parts from Digikey.
>
> Stick a 14500 lithium-ion cell in there instead of the AA for increased
> brightness. These are great for reading laser marking on ICs, also
> inspecting drywall for flatness etc.
>

I like this part of the ad: Emitting Color: black

Arie

Arie de Muijnck <eternal.september@ademu.com> wrote:
> On 2024-03-03 09:16, Jasen Betts wrote:
>
>> Perhaps they buy them on Aliexpress for $2
>> https://www.aliexpress.com/item/33020731608.html
>>
>> Or to answer the implied question, the manufacturers are not buying
>> their parts from Digikey.
>>
>> Stick a 14500 lithium-ion cell in there instead of the AA for increased
>> brightness. These are great for reading laser marking on ICs, also
>> inspecting drywall for flatness etc.
>>
>
>
> I like this part of the ad: Emitting Color: black
>
> Arie
>
>

If you overdrive it enough, it becomes a Darkness-Emitting Diode (DED).

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics