Hello all, I am having a problem moving my circuit from a power supply to a battery. The circuit (I can provide more details if necessary) is basically some
74LSxx IC's which are turned on/off via signal from a PC. The outputs control the state of relays which allow motors to be driven via 12V. To date, I have been doing all my testing using a PC power supply - 12VDC for the motors and 6VDC for the circuit - and this worked perfectly. I (wrongly) assumed it would be a simple matter to change from the power supply to a battery for the power source. I sourced two SLA batteries (1 x 12VDC, 1 x 6VDC) to replace the power supply but the circuit no longer works. The 12V for the motors is working fine. When I run the circuit from the battery, the relays never switch. The circuit is drawing 150mA @ 6V. I can switch from the battery back to the power supply and everything works OK, so I know the devices in the circuit are still working fine. But this is about the extent of my troubleshooting knowledge. I get the feeling I am missing something basic. I thought maybe the 6.4VDC being output by the 6V SLA battery was too high, so I put a 5V voltage regulator in which dropped it to 4.4VDC (I still haven't figured out why so low - but that's another story!) and it still doesn't work. If I leave the voltage regulator in, I can still run fine from the power supply. I thought it may be drawing too much current for the battery, but that doesn't really make sense to me - it's only 150mA. The details of the battery are (I am copying this straight off the battery case):6V 2.5AH Cycle Use: 7.25-7.45V Standby Use: 6.8-6.9V Initial Current: Less than 1.2A
Before I start blundering around blindly with the "insufficient current" theory, is there anyone who could have a stab at this for me and tell me why I can't just switch from power supply to battery?
Many thanks,
Kyle.