georges80
Flashlight Enthusiast
Will, as some of you may know is working on a hall effect based dimmer/controller and while offering some suggestions to him regarding layout etc I asked what hall sensor he was using.
Anyhow, I ended up ordering a few SOT23 versions to play with and then thought it might be useful to folk to have an all in one board that contains a hall sensor, voltage regulator and power FET.
I ran a batch of boards through my PCB house and just received them today. Assembled up one unit (calling them HALLSW) and fired it up. All looks good and some preliminary measurements show it to be a pretty decent performer.
I tested at 5A using 2 parallel P7's as my 'load'. With 5A flowing through the board I measured a 29mV voltage drop across the IN-/LED- connections, so that's about 6milliohms including the FET and solder pads. Not half bad at all :)
Since there's a regulator on the board and also a FET for inverting the drive to the power N-FET there is some quiescent current draw. I measured 60uA which matches with the typical values of the components from their datasheets.
I figure 60uA is pretty low, even 2 months would only drain 60 x 24 x 60uA 0.1 amp.hour from the battery pack.
The regulator is reverse polarity protected. The maximum input voltage to the board would be 25V (the max source/drain voltage spec of the FET). The FET (Q1 in the pic below) is rated above 20A and has a spec of 6milliohms at the gate drive Im using (3.3V).
So, without further ado - heres a picture :). Oh, the scratches on the solder pads are from the croc clips I used to test the board. The PCB is 0.55 x 0.425 (white board) is the HALLSW, next to a penny and a maxflex for size comparison.
The bottom of the board is component free, the intent is to mount the board to the inside of a housing using thermal adhesive tape to transfer heat from the power FET (has a thermal path to the back of the PCB) for folk that are running loads of many amps.
The SW pad on the PCB is intended to be able to be wired to the SWA input of any of my flex drivers, that would provide a magnetic switch input capability. The SW output is an active low signal (when magnetic field is present) and is pulled up to 3.3V via a 100k resistor when no field is present.
I should have units available next week, forgot to order low power fets so I only could build one unit up.
cheers,
george.
Anyhow, I ended up ordering a few SOT23 versions to play with and then thought it might be useful to folk to have an all in one board that contains a hall sensor, voltage regulator and power FET.
I ran a batch of boards through my PCB house and just received them today. Assembled up one unit (calling them HALLSW) and fired it up. All looks good and some preliminary measurements show it to be a pretty decent performer.
I tested at 5A using 2 parallel P7's as my 'load'. With 5A flowing through the board I measured a 29mV voltage drop across the IN-/LED- connections, so that's about 6milliohms including the FET and solder pads. Not half bad at all :)
Since there's a regulator on the board and also a FET for inverting the drive to the power N-FET there is some quiescent current draw. I measured 60uA which matches with the typical values of the components from their datasheets.
I figure 60uA is pretty low, even 2 months would only drain 60 x 24 x 60uA 0.1 amp.hour from the battery pack.
The regulator is reverse polarity protected. The maximum input voltage to the board would be 25V (the max source/drain voltage spec of the FET). The FET (Q1 in the pic below) is rated above 20A and has a spec of 6milliohms at the gate drive Im using (3.3V).
So, without further ado - heres a picture :). Oh, the scratches on the solder pads are from the croc clips I used to test the board. The PCB is 0.55 x 0.425 (white board) is the HALLSW, next to a penny and a maxflex for size comparison.
The bottom of the board is component free, the intent is to mount the board to the inside of a housing using thermal adhesive tape to transfer heat from the power FET (has a thermal path to the back of the PCB) for folk that are running loads of many amps.
The SW pad on the PCB is intended to be able to be wired to the SWA input of any of my flex drivers, that would provide a magnetic switch input capability. The SW output is an active low signal (when magnetic field is present) and is pulled up to 3.3V via a 100k resistor when no field is present.
I should have units available next week, forgot to order low power fets so I only could build one unit up.
cheers,
george.
