Recent content by smev

I have been looking at the AD8277 with built in resistors. More expensive but better CMRR then can be achieved with external resistors. Plus gets rid of 24 resistors on the board. Power is 200ua on the amp. I'm going to get the cell monitoring and isolated communications working first. Then ill...

Take a look at my project, fairly similar http://endless-sphere.com/forums/viewtopic.php?f=14&t=61783

The darlington array is common emitter, and the emitter is tied to same gnd as the mcu. So the base pins will be at the emitter voltage when mcu pins are LOW. The array sinks from the PNP transistors that do the actual cell drain.

The ULN2003 is just a 7 darlington npn array to reduce part counts. When I pull the pnps to gnd to turn on the cell balancers, the voltage can be up to 25.2v which is too much to sink directly on the atmega. Also I'm using one of the npns to switch the circuit on and off. Theres not much out...

I think I might ditch the i2c isolation, its just too expensive and parts are hard to come by. Also by not using i2c we can use the atmega328p through hole. I'm going to try a daisy chained serial isolation, as I can do the serial isolation for much cheaper. So how the protocol would work is...

Looks like the mosfet is a type of FET but with higher impedance. Also it would be nice to use a battery management IC to reduce the resistor count... Unfortunately there is none I can find at a reasonable price. I'm completely open to other solutions rather then the op amps. The celllog 8m...

Well another problem is the op amp resistors that form the voltage dividers, they cannot be too high of a value or the op amps don't play nice. So there will always be some drain there. Unless the gnd is disconnected, theres going to be at least 0.5ma wasted just by the op amps. I think the...

Well the real gnd is the negative on the battery, the atmega and opamps are essentially the load for the mosfet. The schematic may be a little confusing with how I have the gnd net. When power is applied to the enable pin, the optocoupler switches the npn to start sinking current to the battery...

The gnd is cut by the MMBT2222A-TP NPN transistor should be a almost non-existant leakage (T7). The schematic has the npn where it grounds back to the battery. I can put a timeout on the microcontroller to make sure the bms is always shut down. How this setup would work is one atmega would be...

Yeah I don't think its going to be that efficient on the power usage. The atmega will probably pull 10ma on its own. And if driving the shunting mosfets its going to need some extra power. So just going to the route of cutting the gnd when not in use so power usage shouldn't matter too much. I...

Yeah I was wondering about the input diodes. I'll remove them from the inputs. Maybe I'll put some diodes on the power to allow for lower cell count packs. As far as components, part selection hasn't properly been done. Components were just mostly selected because they were in the eagle...

And here is the shunting board schematic. The cell monitor would mount to this board bed of nails style. The shunts are controlled by the output pins of the isolated microcontroller.

Here is a rough schematic of the cell monitor board. I still need to calculate a few resistor values, but for the op amp resistors they will be all the same value, around 100k ohm. Also not all parts have been selected yet. So the ICs might change a bit. I am using the atmega644 for prototyping...

Ok so in search of a easier way to manage lipo batteries, I have decided to design my own bms system. I would like to get a production run done of some nice smd boards. So pretty much looking for how many people would be interested in purchasing. What each board would do is have a read out of...

Another note, the blower seemed have a lot more power on the dc then the ac at 100v. It would probably be sufficient to run at around 50v and the lower voltage would solve a lot of problems.