Sallen Key Low Pass Filter, bandpass filter

[Maglatron]

ok I'll get the readings, thanks but since, I havn't changed the setup of the LM3914's from when I changed the 10nF's to the 100nF's and when I was on the 10nF caps none lit, does this information add to the equation?

 

[Maglatron]

Mr Bertus, did you read the last comment when I said

havn't changed the setup of the LM3914's from when I changed the 10nF's to the 100nF's and when I was on the 10nF caps none lit

??
will still get the readings later today!

 

[Maglatron]

after the 1k resistor?

hello,

measure the voltage on the inputs of the lm3914's (pin 5)

bertus

 

[Maglatron]

so I measure between the voltage between pin 5 and pin 4 on the left handside of the circuit? thanks I'll check for continuity between pin 5 and pin 6 too!

 

[Maglatron]

resistance between 5 and 4 = 7.11Mohm and between 5 and 6 = 7.11Mohm so no short on the 5 to 6 but the chips LM3914's are getting really hot and when the cicuit is on pin 5 to 4 and 6 respectivly 11.79volts which might I add that that is the voltage of the battery! not sure whats wrong? help !!

 

[bertus]

Hello,

I assume you connected pin 2 (V-) to the minus of the power supply and pin 3 (V+) to the plus of the power supply.

Bertus

 

[Harald Kapp]

not sure whats wrong?

Your wiring? Check it, then check it again.
Check the polarity of the electrolytic capacitors C1 and C2

Here's how I do it:
- make a copy of the schematic
-trace every single connection, mark on the copy when o.k.

What's left is obviousy not o.k.

 

[bertus]

Hello,

An other tip is use different colors of wire.
For example:
Positive power red.
Negative power black.
Ref blue.
Analog signal yellow.
Digital signal brown.

Bertus

 

[Maglatron]

got pics soon but, I will check that the plus and minus are correctly orientated but I think they are

Your wiring? Check it, then check it again.
Check the polarity of the electrolytic capacitors C1 and C2

Here's how I do it:
- make a copy of the schematic
-trace every single connection, mark on the copy when o.k.

What's left is obviousy not o.k.

thank you for that I'll draw out the circuit and mark off each connection I've got extra board so I'm just going to start again it'll be easier because when looking from the top and the bottom of the board gets confusing, also does the signal coming from the filters be yellow (analog signal wire) I don't think there are any digital signals in this circuit

 

[bertus]

Hello,

You could see the leds as digital signals as they can only be on or off.

Bertus

 

[Maglatron]

not that there's much point but for your viewing pleasure

 

[Maglatron]

next I'm going to disconnect the signal and see if they still light and going to see weather the power source is backwards then if that doesn't work I'm going to start afresh shouldn't take too long I would do the suggested (draw it out) and debug but could probably build a new one in the time that takes! Where I put the power and gnd to the LM3914 circuit is either side of C1

 

[Maglatron]

I just took of the signal to pin 5 and all the lights lit still and power cables were correct so took all wires off of the board at that part of the circuit and I will do the suggested with the wire colours and I will expand out to the left so the connections are not so tightly packed together and be more easy to see. thanks

 

[Maglatron]

so I just had a thought perhaps there is something wrong with my REF GND circuit how do I test that please? because when I dettached the signal I still had the REF GND connected and the LED's were lit!?

 

[bertus]

Hello,

The output voltage of the ref circuit should be about half the power supply voltage.
You measure it between the minus of the power supply and the ref output.

Bertus

 

[Maglatron]

( pins 6 and 7 on chip 1 and on chip 2 pin 8) should be yellow?? (9 and 3 on both chips red,) on chip 1 (pin 4 and pin 8 blue ) and (one more blue after the resistor that comes from the junction of 6 and 7 of chip 2) and (on both the chips 2 is black?) (and pin 5 on both chips yellow?) (pin 9 of both red)

 

[bertus]

Hello,

I think you mean the pins 6 and 7 of chip 1 and the pins 4 and 8 of chip 2, that are static analog signals, so that could be yellow.
Take some color markers and draw the colors in the schematic, by following the lines.

Bertus

 

[Maglatron]

thanks missed the pin 4 of chip 2 can't print atm

 

[Maglatron]

so the battery voltage is 11.55v and the ref cicuit measure is 3.8volts is this fine? started colour coding the circuit will finish tomorrow and take pics!

 

[bertus]

hello,

no, that is not correct.
when the battery voltage is 11.55, i would expect the ref voltage to be about 5.77 volts.
are the resistors of the voltage divider the same value?

bertus