Hi
I have just built a digital readout for my milling machine using a design available on the web, and I have built a battery backup for it using a design from the same source. While the battery backup works well I would like to extend the battery life if I can.
At the moment data from the milling machines three capacitive scales is transmitted at 3.3 V to a MSP430G2553. The battery backup uses two Schottky diodes and a capacitor and keeps the scales powered so they don't lose track of their position while shutting down the MSP430G2553.
When running on the battery the current drawn is about 700uA but if I disconnect the three data lines to the MSP430G2553 then the current drops to about 35uA. The battery backup is from AA cells which would give the batteries a life of about 4 months. I'd like it to be over a year if I can and my initial idea is to use a 74HC08 to disconnect the data lines when running on battery. In that idea one input for each gate would come from the main power supply and the other from the data lines coming from the scales. The chip would be powered from the battery.
After thinking about it a bit I am less certain about this. The power consumption would only be reduced if the input currents were very low. I wondered about a 74 series buffer instead. What I would like is something that works like a triple pole normally open 3.3V relay.
I'd welcome any advice.
Russell
I have just built a digital readout for my milling machine using a design available on the web, and I have built a battery backup for it using a design from the same source. While the battery backup works well I would like to extend the battery life if I can.
At the moment data from the milling machines three capacitive scales is transmitted at 3.3 V to a MSP430G2553. The battery backup uses two Schottky diodes and a capacitor and keeps the scales powered so they don't lose track of their position while shutting down the MSP430G2553.
When running on the battery the current drawn is about 700uA but if I disconnect the three data lines to the MSP430G2553 then the current drops to about 35uA. The battery backup is from AA cells which would give the batteries a life of about 4 months. I'd like it to be over a year if I can and my initial idea is to use a 74HC08 to disconnect the data lines when running on battery. In that idea one input for each gate would come from the main power supply and the other from the data lines coming from the scales. The chip would be powered from the battery.
After thinking about it a bit I am less certain about this. The power consumption would only be reduced if the input currents were very low. I wondered about a 74 series buffer instead. What I would like is something that works like a triple pole normally open 3.3V relay.
I'd welcome any advice.
Russell