Search found 170 matches
- Sun May 22, 2016 2:59 pm
- Forum: General Discussion
- Topic: op amp summing question
- Replies: 3
- Views: 4078
Re: op amp summing question
In essence they are the input voltages multiplied by their relevant gains being added, if we call the top input resistor R1, the bottom R2 and the feedback resistor Rf, substituting them for say 1K and 500R resistors and x for the unknown input voltage we end up with: (1v * (Rf/R1)) + (x * (Rf/R2)) ...
- Sat May 21, 2016 11:45 pm
- Forum: General Discussion
- Topic: op amp summing question
- Replies: 3
- Views: 4078
Re: op amp summing question
Remember that in that configuration the output will be trying to make the -ve input of the chip 0v. If the resistors were all the same size you'd have the nice simple equation where the two input voltages will equate to the inverse of the output voltage. I think as you have half the resistance on on...
- Mon May 02, 2016 4:19 pm
- Forum: General Discussion
- Topic: DIY Traffic Light System
- Replies: 5
- Views: 5727
Re: DIY Traffic Light System
I don't know about how much volt drop you'd get over that sort of distance on something as small as telephone wire, it may be you need some sort of electronic amplifier in there to overcome this.
- Sun Apr 03, 2016 11:13 pm
- Forum: General Discussion
- Topic: Converting guitar pedal -9v DC adapter (mains) to 9v battery
- Replies: 4
- Views: 4661
Re: Converting guitar pedal -9v DC adapter (mains) to 9v bat
Feedback is where you have a complete loop and it feeds back into itself i.e. a microphone near a speaker which causes a squeal. I don't see any reason why a 9v pp3 will cause this, nor why 6xAA doesn't. Both will provide DC as smooth as a baby's bum (the voltage is from a chemical source, not deriv...
- Sun Apr 03, 2016 3:47 pm
- Forum: General Discussion
- Topic: Converting guitar pedal -9v DC adapter (mains) to 9v battery
- Replies: 4
- Views: 4661
Re: Converting guitar pedal -9v DC adapter (mains) to 9v bat
What is the spec of the adaptor?
You say -9v in the title so it is making me think you may have your polarity incorrect. To get -9v with centre pin 0v you need to connect the positive of the 9v battery to the centre pin and negative to the outer barrel.
You say -9v in the title so it is making me think you may have your polarity incorrect. To get -9v with centre pin 0v you need to connect the positive of the 9v battery to the centre pin and negative to the outer barrel.
- Sun Feb 28, 2016 4:43 pm
- Forum: General Discussion
- Topic: LDR Project
- Replies: 4
- Views: 3472
Re: LDR Project
If you want a more on/off switch then consider a darlington pair transistor. The BC547 has a gain of 110 to 800 which will depend on the voltage at it's base-emitter and a collector current of 100mA. Darlington pairs have a much higher gain.
- Sun Feb 21, 2016 4:04 pm
- Forum: General Discussion
- Topic: Help Required - Slide Potentiometer
- Replies: 10
- Views: 5982
Re: Help Required - Slide Potentiometer
Just in general, volume control in amplifiers for sound is usually log. He'll just need to double check as a linear slider fitted where a log one ought to be won't work very well.
- Fri Feb 19, 2016 10:54 pm
- Forum: General Discussion
- Topic: Help Required - Slide Potentiometer
- Replies: 10
- Views: 5982
Re: Help Required - Slide Potentiometer
Also pay attention to wether it is linear or logrithmic, (lin or log), volume controls are usually log.
- Sun Feb 14, 2016 5:48 pm
- Forum: General Discussion
- Topic: can someone help with a project
- Replies: 5
- Views: 3388
Re: can someone help with a project
I don't think AC will work, AC is a constantly changing sine wave - iirc the high voltage pulse needed is create by an instantaneous drop in voltage causing a back emf.
- Tue Jan 26, 2016 4:55 pm
- Forum: General Discussion
- Topic: can someone help with a project
- Replies: 5
- Views: 3388
Re: can someone help with a project
An ignition coil and a relay, what is providing the 450 pulses? You may need an ignition amplifier to fire the 12v to the coil.