Are there any solid state options available for a simple relay for a 9v battery backup?
Power to the device will be DC +5V. If this voltage drops below a specified level, say 2.5V, a relay should switch to a 9V battery backup (with a voltage regulator, of course).
I've done some searching but I'm having trouble coming up with something like a part number or datasheet.
Are there any solid state options available for a simple relay for a 9v battery backup?
Power to the device will be DC +5V. If this voltage drops below a specified level, say 2.5V, a relay should switch to a 9V battery backup (with a voltage regulator, of course).
I've done some searching but I'm having trouble coming up with something like a part number or datasheet.
So a blocking diode has a higher current rating than a normal diode and will block current flow when one side has a higher voltage than the other?
So if I have 5 volts on both sides (one Vcc and one the regulated 9V), and I put a blocking diode in series with the backup and then connect the two sources in parallel, the 5V backup source will be enabled when Vcc drops below 5V?
So a blocking diode has a higher current rating than a normal diode and will block current flow when one side has a higher voltage than the other?
So if I have 5 volts on both sides (one Vcc and one the regulated 9V), and I put a blocking diode in series with the backup and then connect the two sources in parallel, the 5V backup source will be enabled when Vcc drops below 5V?
hi,
Assume that the current required by the load is less than 1A.
By connecting a 1A diode [1N400x] from the +5V to the load will give approx 4.7V at the load.
Do the same for the output of the regulated +5V, that is connect a 1N400x diode in series with the 5Vreg out and the load.
Post a sketch showing the basics on how the 5V and the 5Vreg are going to be used and I will draw in the diodes..
A 9V battery cannot properly power a 7805 regulator. The regulator needs a minimum input of 7.5V but the voltage from a 9V battery quickly drops to 7.2V then drops slower to 6V.
Use a low-dropout regulator that will still provide a regulated 5V when its input is as low as 5.5V.
A 9V battery cannot properly power a 7805 regulator. The regulator needs a minimum input of 7.5V but the voltage from a 9V battery quickly drops to 7.2V then drops slower to 6V.
Use a low-dropout regulator that will still provide a regulated 5V when its input is as low as 5.5V.
t the datasheet for a 9V alkaline battery. Its voltage quickly drops to 7.2V.
Look at the datasheet for a 7805. it is spec'd with an input of at least 8V. Its dropout voltage is typically 2V but could be higher. When it has dropped out then it is not regulating.
Power to the device will be DC +5V. If this voltage drops below a specified level, say 2.5V, a relay should switch to a 9V battery backup (with a voltage regulator, of course).
A relay with a 5v coil will probably drop out at 3v. If this is close enough to 2.5v, and relays with 5v coils can handle your current draw requirements then hook up the relay contacts so the 9v batt/reg arrangement is switched in when the relay drops out.
t the datasheet for a 9V alkaline battery. Its voltage quickly drops to 7.2V.
Look at the datasheet for a 7805. it is spec'd with an input of at least 8V. Its dropout voltage is typically 2V but could be higher. When it has dropped out then it is not regulating.
I have a 12v DC paging transmitter. Want to create a battery backup power supply using a 9v battery. So when I lose 12v the 9v takes over. Any thoughts?