|\
L7805 output -> |+\_____ 5V buffered supply
|-> |-/ |
| |/ |
|-------|
Buffering is for signals- where the power is not as important as the clarity, and for some reason or other the signal's original power is not able to get through because it lacks the power to do so (overcome capacitances, inductances, noise or other imperfections on the line). Buffering is not for powering things.
OP AMP Operation:
The circuit below shows a simple buffer circuit. The input impedance of an op amp is extremely high (on the order of 10^12 ohms). It might be used if the input signal to the op amp was coming from a source which could supply almost no current. The output of the op amp can easily drive 1000 ohms or more.
It is time for you to attach the entire schematic diagram of your project. PNG or GIF format is preferred.
Did you measure that with the load connected?Right, I'm not having a good time. Outside of the fact I'm down to one battery with >7.5V voltage left
Did you measure that with the load connected?
The voltage will drop significantly on load.
1. Connect the 32768 Hz crystal directly to TIMR1 's osc and you can get rid of the 4040.
2. Connect the LEDs directly to the PIC (It can easily drive LEDs) gets rid of the weak 4016
3. Get a programmer with debug support like a PICkit2 and maybe you wont need the debug LEDs
Warning, the 7805 and everything else will heat up the LM35 and skew your temperature readings if they are on the same PCB or anywhere near each other.
Also the expensive 2915 LED display will chew through batteries in no time at all. An LCD will draw much less current. I built a thermostat prototype using a 16F917 with built in LCD glass driver and it works like a charm.
Look at the datasheet of the LM35. Its supply current is almost nothing. Look at the datasheet to see that maybe it is connected backwards so of course it uses a very high current and might be destroyed.
Power it from a 9V 600mA wallwart instead of a 9V battery and it will probably be fine. The display needs a minimum of 4V for the LEDs and 3V for the logic so it's not surprising that it works half assed on 3.3VNo I didn't - thanks. My current status is that only half the display worksThe unloaded voltage is 8.15V, the voltage on load is about 4.9 V and 3.3 of that is finding its way to the display and PIC.
Power it from a 9V 600mA wallwart instead of a 9V battery and it will probably be fine. The display needs a minimum of 4V for the LEDs and 3V for the logic so it's not surprising that it works half assed on 3.3V
If you are hung up on using batteries, use 6 AA alkalines or 7 AA NiMhs in series.
with three AA cells, why not just omit the regulator?
Most PICs can withstand 6.5V for sort lengths of time so you could probably use four AA cells would be fine, but check the datasheets of alll the ICs before tying it.
That sounds very strange. Make sure that all the display grounds (LED and Logic) are connected properly. You might want to double check this with an ohmmeter to rule out any breadboard problems.I've got the other half of the display back - well, sort of. If I put a logic 0 on the BLANK input (pin 19), the left half (only) of the display works. If I put a logic 1 there, the right half (only) works.
That sounds very strange. Make sure that all the display grounds (LED and Logic) are connected properly. You might want to double check this with an ohmmeter to rule out any breadboard problems.
Also, make sure that the 5V supply rails are properly bypassed with some 0.1uF caps and a 22-100uF cap as well.
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?