The post explains a simple, single chip digital potentiometer circuit which can be controlled through a single pushbutton, a dual pushbutton (up/down) or even through external digital (CMOS/TTL) input triggers.
About DS1869 Dallastat
TM is a rheostat or potentiometer. This unit delivers 64 conceivable consistent tap outputs over the over-all resistive spectrum.
The typical resistive stretches are 10 kΩ, 50 kΩ, and 100 kΩ. The Dallastat may be governed by both a mechanical switch contact closure input or simply a computerized reference input for example a CPU.
The DS1869 functions from 3V or 5V supplies. Wiper setting is sustained without having power by means of a EEPROM memory cell range.
The EEPROM cell array is going to endure higher than 50,000 writes. The DS1869 can be obtained from two regular IC packages such as an 8-pin 300-mil DIP and an 8-pin 208-mil SOIC.
The DS1869 could be set up to function employing an individual pushbutton, combined pushbutton or electronic base input by switching power-on setting.
This is drawn out in Figures 1 and 2. The DS1869 pinouts enable entry to each ends of the potentiometer RL, RH, in addition to the wiper, RW.
Control inputs contain the digital reference input, D, the up contact input, UC, and the down contact input, DC. Supplementary pins incorporate the positive, +V, and negative, -V, supply inputs. The DS1869 is stipulated to function from -40°C to +85°C.
Main Features and Pinout Details:
Simulation and Working
The DS1869 could be custom made to execute from an individual contact closure, twin contact closure, or a digital root input. Figures 1 and 2 depict the two contact closure variations.
Contact closure is considered as a changeover from an increased level to a reduced degree on the up contact (UC) or down contact (DC) inputs.
All three control inputs are busy while in a low status and are sedentary while in a high disposition. The DS1869 interprets input pulse widths as the method of regulating wiper motion.
One pulse input on the UC, DC, or D input terminals will result in the wiper placement to relocate 1/64th of the entire resistance.
A changeover from a high to low on these inputs is regarded as the outset of pulse process or contact closure. One pulse has to be more than 1 ms nevertheless running not anymore than 1 second. Pulse timings are presented in Figure 5.
Recurring pulsed inputs may be used to approach via every resistive placement of the unit in a typically rapid technique (see Figure 5b).
The necessity for frequent pulsed inputs is because pulses needs to be split up by optimum time of 1 ms. In the event that the input is not permitted to be sedentary (high) for a minimum of 1 ms, the DS1869 will probably read repetitive pulses as just one pulse.
Pulse inputs continuing more than 1 second will result in the wiper to relocate one place every 100 ms following the preliminary 1-second store time.
The complete time to transcend the whole potentiometer employing a nonstop input pulse is presented the equation below:
≈1 second + 63 X 100 ms = 7.3 (seconds)
The proposed digital potentiometer circuit can be understood in-depth from the following pdf attachment.