This is just a guess. It be better if someone more knowledgeable confirmed it.
In this post Buck and Boost Drivers, Testing, Modding, and Discussion (Pic Heavy) - #20 by Jensen567
Cutting the trace after the 47k resistor leaving the opa333 is my guess. In the datasheet tps61088 it shows a typical application where the voltage divider is by it’s self (fully on). I’m assuming the opa333 controls voltage the resistor divider is reading to control voltage feedback and modes from the pic.
Just a guess :question:
This could work but with how the remaining divider (R1, R2) is set up, it is only voltage regulated and it will put out ~6V and kill a 3V LED.
You’d have to set up the ILIM pin of the TPS61088 correctly.
With the stock 10k for R4, it means practically no current limit. This needs to be changed!
The H1-A driver changes mode only if less than 2 seconds have passed since last power cycle or so. Under normal operating conditions this means you can leave it at whatever mode, turn it off and on and it will remain the same.
As a tinkerer I can understand Funner's viewpoint but, is it worth such effort?
Bear also in mind that if you leave the driver with just one “high” mode, I advice you to select a current output your flashlight can handle without cooking the emitter or overheating above what you may consider permissible, even in tailstanding condition if applicable.
That’s exactly how to do it kikkoman. And yes, thermal throttling (if it does it) will be disabled on the PIC. Only the Boost IC overtemp. protection can then save it.
Thanks for explaining the possibility to switch the H1-A with a momentary button.
I plan to switch modes with an external microcontroller. Basically i only need two modes (33% and 100%) and i want a microcontroller or bluetooth remote to switch through the modes for me. By chance do you know the voltage and current of the pcb trace, which needs to be cut? I could measure it myself, but the driver is still in shipping.
Here is an recent image from a H1-A driver ordered 01/2019.
I need to find a way to have only two modes 33% and 100%. Because i don’t have any idea how to program a PIC, i had the idea to use an external microcontroller to switch through the modes for me. The MCLR pin seemed to be a good solution. Pulled to the ground, the PIC should do a software reset. Therefore i desoldered the MCLR-Pin from the board and pulled the pin temporarily to ground. But nothing happens. The driver just works as before.
Besides a custom firmware, which would be great, do you have any idea how to get only two modes?
Here’s a driver which will run an LED from body heat using a TEG or Peltier stack. Input voltage polarity does not matter and I found it works well. Custom Thermoelectic and TXL Group sell these boards for $19US or you can get the unipolar version for only $14 (it has half the component count).
And here’s another energy harvesting driver which will run an LED off of body heat via a Thermoelectric Peltier or TEG, only 25mV required! The resistor and capacitor in center can have two different value pairs, depending on the design revision. The caps with question marks need to be pulled off the board and measured out of circuit. They’re 0402 parts! You can buy the PCB for only $12 from the usual electronics component distributors.
Quick question fellows, does anyone knows which type of reverse polarity protection MOSFET the H1-A driver employs? It's the small 3 pin thing at the board backside, just g00gl€d the markings but no hits. The usage of such small MOSFET is also a tad strange to me, it totally looks inadequate given the amount of input current it should handle.