Li-ion power mod
Posted: Sun Apr 02, 2017 12:10 am
I like this little scope for it can be a great tool for low frequency work. Biggest selling point to use it over the big proper scope is that it is small and portable.
Except it's not quite portable if you also need to carry a power source and look for an outlet, now is it?
Well I decided to fix that:
I used a separate charger board with protection and a step-up module built on fp6291 high frequency pwm DC converter IC. I had to swap the resistor in the feedback divider to 130k (circled on the pic) to bump output voltage from 5v to 8.4v:
Also I modified the main board so that I could use the built in power switch. It was quite easy, just cut two tracks to the switch and add a jumper bypassing the protection diode (we don't want to waste 0.7v there, also bringing the voltage on par with what 9v with a diode would be):
Now to add a bit of thermal glue to stick the modules on the enclosure and add a cut in the bottom panel for the charging port:
Stick the battery pack on the back of the case with some double sided tape and tidy up the wiring to complete the whole thing. I now have an awesome portable scope:
If you want to buy the same things I used here are the links:
I also recommend to recharge early because even though the charge controller has over discharge protection, it's quite low at 2.5v. You shouldn't let your li-ion battery fall below 3.0v, unless it's specifically rated for low discharge.
If you use another step up module, make sure it's switching frequency is high. With the one I used VCC ripple (a few mV at 1mhz) has no noticeable effect on the waveform acquisition because it's much higher than the bandwidth of the scope. With a lower frequency switching module you most likely will have to fight the ripple with some caps and filters.
Wishlist:
Except it's not quite portable if you also need to carry a power source and look for an outlet, now is it?
Well I decided to fix that:
I used a separate charger board with protection and a step-up module built on fp6291 high frequency pwm DC converter IC. I had to swap the resistor in the feedback divider to 130k (circled on the pic) to bump output voltage from 5v to 8.4v:
Also I modified the main board so that I could use the built in power switch. It was quite easy, just cut two tracks to the switch and add a jumper bypassing the protection diode (we don't want to waste 0.7v there, also bringing the voltage on par with what 9v with a diode would be):
Now to add a bit of thermal glue to stick the modules on the enclosure and add a cut in the bottom panel for the charging port:
Stick the battery pack on the back of the case with some double sided tape and tidy up the wiring to complete the whole thing. I now have an awesome portable scope:
If you want to buy the same things I used here are the links:
- Charging controller (5 of them for dirt cheap): http://www.ebay.com/itm/5pcs-Micro-USB- ... tkn=iOtp8j
- Step-up module: http://www.ebay.com/itm/112064300397?_t ... EBIDX%3AIT
- Battery pack: http://www.ebay.com/itm/3-7V-4000mAh-Li ... SwRgJXlbYJ
I also recommend to recharge early because even though the charge controller has over discharge protection, it's quite low at 2.5v. You shouldn't let your li-ion battery fall below 3.0v, unless it's specifically rated for low discharge.
If you use another step up module, make sure it's switching frequency is high. With the one I used VCC ripple (a few mV at 1mhz) has no noticeable effect on the waveform acquisition because it's much higher than the bandwidth of the scope. With a lower frequency switching module you most likely will have to fight the ripple with some caps and filters.
Wishlist:
- Bare li-ion pack hanging out is no bueno, it can get punctured and then it's galaxy s7 all over again. I would like to add some cover for it, ideally a 3d printed one with a backstand.
- Maybe when the firmware sources are released it can be hacked to use one of the unused controller pins to monitor battery voltage, that would be awesome.