Previously I used a linear regulator, now I use Max756 ( ) boost converter. I`m seeing 0. 1 - 0. 3V output ripple in the current. The Max756 datasheet says I should expect about 50 mA ripple. So my power is a little noisier than expected, but my real problem is when powering a microphone (plugged into sensor1) I see 2. 4V of ripple. This just isn`t acceptable for my needs.
Click here to download the full size of the above Circuit.
Here is my scope output (blue is power signal and yellow is mic output while it`s quiet): First, your microphone amplifier has a gain of 100 and sees ripple on the power supply exactly the same as a signal from the microphone. You need to heavily filter the supply going to the microphone and amplifier circuit. First thing, add a bigger capacitor (maybe 10 uF) in parallel with the 100 nF bypass capacitor on the breakout board. Then add a resistor or inductor in series with the Vcc line from the main board to the microphone breakout board. Your second problem is that your switch frequency is too low. The switching frequency is 10 kHz - you are just never going to get good audio performance with a 10 kHz switcher anywhere nearby. If you look at the data sheet, the pulse frequency drops with load current. It looks like this particular boost converter has a fixed duration `on` time, and changes the off time to vary the duty cycle as needed. Your circuit is drawing relatively low current so the pulse frequency is very low. You would prefer to have a style of regulator that works by pulse width modulation: the pulse frequency is constant, but the `on` time is varied to regulate the output voltage. Alternately, look for a regulator of the same style that works at a higher frequency under your actual load current. 100 kHz is easier to filter from the supplies, easier to filter from the audio path, and inaudible even if a bit makes...
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
characters left: