AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Pt2399 simple delay schematic1/25/2024 ![]() Note also that the value of the capacitor will have an effect on the amount of ripple as well as how long it takes the capacitor to charge. The value of this voltage depends on the duty cycle. Note how it just looks like a steady DC voltage. The output of the smoothing capacitor is shown below (the input is just the output of the previous plot). This will make it so that the current sinked through the transistor is consistent, resulting in a steady delay time. We will now discuss each of the steps and what each component in the schematic is doing.Īfter the voltage divider, a large value capacitor is used to smooth the square PWM signal into a continuous DC signal. Set a resistor to regulate current range and set a minimum delay time to prevent chip lockupīelow is a basic schematic showing how this is done. Shift overall signal level from 0 to +5V to 0 to +2.5V to match pin 6 voltage levelĪpply signal to the base of a transistor that acts as a variable resistance from pin 6 to ground In order to use the PWM, we need to do a few things: The PWM output cannot be used directly, but with the use of a couple of common components, we can do some very clever things. A 50% duty cycle will hold the output at +5V for an amount of time and then at GND for an equal amount of time. A duty cycle of 100% is a constant 5V DC output. ![]() PWM is specified by the duty cycle (or percentage of time) that the signal is held high. PWM is where an output pin of the microcontroller is switched between high and low (typically +5V and GND) very quickly. It's not a huge deal, but some people are cost sensitive.Īnother approach that can be used is to use the pulse-width modulation (PWM) output from the microcontroller. This can require calibration or acceptance of the fact that there will be some variation.Ĭost: Digital Potentiometers are another component and are typically even more expensive than the microcontroller used. Tolerance: Digital potentiometers can have tolerances up to +/-20%, which can make precise determination of delay time difficult. The advantage here is that it works very much like an analog potentiometer and it is relatively easy to work with.ĭespite the functionality of this approach, there are some drawbacks that I personally don't like, including: The serial communication is used to configure the internal arrays of resistors between the wiper and the two lugs. A digital potentiometer is an integrated circuit that has pins for the three standard pot lugs, power, ground, and serial communication. The approach used by the Taptation and advocated by many is the use of a microcontroller that controls a digital potentiometer. As current decreases, delay time increases. Note that as we increase the resistance, Ohm's law states that the current must be reduced because we have a constant voltage. This is achieved in most PT2399 delays with the use of a B50k potentiometer wired as a variable resistor and a small fixed resistor to prevent chip lockup. An internal +2.5V voltage is applied to pin 6, so the resistance placed from pin 6 to ground will determine how much current passes through it. The delay time for the PT2399 is set by the amount of current that is sinked through pin 6. If you want even more detail, I highly recommend studying the fantastic PT2399 analysis at Electrosmash. In order to understand the hows and whys of this, let's talk a little bit about how the delay time is set on the PT2399. Software Debouncing: Other solutions may include software debouncing, but the ones I have seen tend to use a debounce scheme that eats clock cycles and therefore limits how fast you can tap in. Hardware Debouncing: Most solutions don't implement hardware switch debouncing, which helps make for more accurate tapped in tempo Default firmware allows for the original tapped in tempo as a quarter note as well as dotted eighth and eighth notes.Įasily modified: The code is all in Arduino, so it's easy to customize it for what you want it to do Time Division Switch: Easily configured switch for dividing the tempo. Relative time adjustments: Adjust your time relative to the tapped in tempo. In addition to being DIY and inexpensive, the project presented here has some great features, as well, including: This issue can all be remedied with the use of one of the many ubiquitous microcontrollers out there. ![]() There are a couple of commercially available solutions, such as the Taptation found at, but where's the fun in that? This is DIY, after all. However, with all its advantages, it doesn't have an easy tap tempo function. It is a digital IC, but it is implemented much like any other analog component into various circuits. The PT2399 chip has been the go-to standard for DIY delays for years.
0 Comments
Read More
Leave a Reply. |