Do you have a load between the cathode of the diode and the neg terminal of the battery (other than the internal resistance of the voltmeter)? The meter resistance is high, probably >20megOhm, so the current being drawn through the diode is likely less than 400nA. Try again with currents between 1mA and 1A flowing through the diode.
That's a generality for normal operating currents where the forward drop is typically about 0.65-0.7v, but it varies from that with current (look at a data sheet for curves showing this). Ignoring the diode resistance, its drop is actually logarithmic versus current. Since a typical multimeter has a 10MΩ input impedance, the diode current for your measurement is only about 0.9 micro-amps, and at that low current the diode apparently only has a forward drop of about 0.3
I get expected reading if I put a diode and 220 Ohm resistor in series with the battery and measure the voltage across the diode. It was exactly 0.7 volts.
I wanted to know this so I can use a 6V battery with PIC by using a diode in series.
According to the datasheet, the absolute maximum rating is 6.5V (see page 131) so running at 6V isn't exactly good for it but it shouldn't do any harm especially if it's for short periods and 5.7V is safer still. https://www.electro-tech-online.com/custompdfs/2010/03/16f628a.pdf
If you're intending to use four AA cells, I say stick the diode in series and it'll also serve as an idiot diode as well as a voltage dropper.
According to the datasheet, the absolute maximum rating is 6.5V (see page 131) so running at 6V isn't exactly good for it but it shouldn't do any harm especially if it's for short periods and 5.7V is safer still. https://www.electro-tech-online.com/custompdfs/2010/03/16f628a-1.pdf
If you're intending to use four AA cells, I say stick the diode in series and it'll also serve as an idiot diode as well as a voltage dropper.
Quite true. Thanks !! I guess I will go with that.
Its for my bot which I intend to run on a 6V 4.5 AH SLA battery.
So I will have the diode in series for the uC portion so that it gets 5.3 volts.
The 78L05 I have been using was forcing me to use a 9V + battery.
be safe to protect the chip
you can afford one LM1117-5 LDO regulator for 6V input.( provided 6V is stable .
though the package is different, it can be adopted on solder side.
Otherwise work with 3 dry cells at 4.5V
PIC works well at 4.5 or even 3.8V till the cells discharge.
Quite true. Thanks !! I guess I will go with that.
Its for my bot which I intend to run on a 6V 4.5 AH SLA battery.
So I will have the diode in series for the uC portion so that it gets 5.3 volts.
The 78L05 I have been using was forcing me to use a 9V + battery.
Unfortunately the voltage of a 6V SLA can be as high as 7.2V when hot off the charger so you'll need at least a couple of diodes to drop the voltage to a safe level.
A LDO regulator is a better option but more expensive.
Unfortunately the voltage of a 6V SLA can be as high as 7.2V when hot off the charger so you'll need at least a couple of diodes to drop the voltage to a safe level.
A LDO regulator is a better option but more expensive.
as we do testing and make a project ( not a bulk manufacturer), a one off would always help, instead of killing a microchip.
somehow the series drop methods are worth LM2931 series also have 5V with
Another nit: If you are using the ADC or any other parts that require a fixed, and known Vcc, the regulator will keep the Vcc within a few mV, while all the schemes using dropping diode(s) will cause the Vcc to vary by at least 1.5V as the battery discharges.