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MAX8881 and DS2490 Characterization for Cells

Rechargeable AA cells are very popular for a large variety of portable applications. The number of brands is also high, and the cell quality can differ considerably. Cell capacity is sometimes different from that specified, and the capacity often deteriorates dramatically after a limited number of discharge cycles. ….

See Maxim Application Note – Simple Characterization Circuit for Rechargeable AA Cells

This characterization circuit, plus a PC and some software, accurately measures the full discharge cycle for a rechargeable AA cell. Cell capacity and output resistance can easily be determined from the curve resulting from these measurements.

MAX8881 and DS2490 Characterization for Cells

In Figure 1, the simple circuit is connected to the USB port of a PC. No external power source is required because power is extracted from the USB bus voltage. U1 (DS9490R) is a USB dongle that converts the USB protocol to the 1-Wire® protocol, thereby allowing the PC to communicate with the key circuit component (U2).

Temperature Controller for Cooling Chamber

This is part of an user manual i used to give for cooling controllers – app007.pdf

The Logic of cooling in temperature control is inverted, Activating the relay powers a compressor which cools the system. A small modification at the output stage, makes any heating controller into a cooling controller. It can also be done with external relay logic, but make sure on power failure (control power line) the compressor ( 3 ph power) shuts down. In all heating and cooling control, when a broken or disconnected sensor is detected, the controller should turn off all outputs and indicate a fault condition.

Cooling Controller

Before you use a Controller to Cool a Chamber to Say +5 Deg C.

First :

Do not Connect the Controller. Directly Connect the Cooling Device e. g. : Compressor. to the system and check the maximum cooling it can produce. In case temperature goes to 0 deg or -10 deg then by using a STC1000 you can control at +5 deg.

But if directly you get cooling of only upto +10 deg then it is impossible for any controller to produce extra cooling, in such a case as this use a better compressor or more insulation.

Second :

Connect Sensor properly and replace when broken keep sensor close to the source of cooling.

Third :

Deadband (DB) at minimum is 1 Deg this is the best setting, maximum setting of deadband may increase compressor life and also save power but will produce a huge variation in temperature.

Fourth :

If large Variation of temperature is present and you need accurate control Reduce deadband to min.

Unit is factory set db at 1 deg, remove seal tape before dead band adjustment.

Analog Circuits – delabs Circuits

Analog Circuits – delabs Circuits

Analog Circuits added after 2004

Analog Circuits Instrumentation

Circuits in Above

  • Voltage to pulse converter, for impulse counter
  • Current Source mA for calibration
  • AC voltmeter digital
  • 8 channel analog mux with sample hold

PNG Circuits – Analog Related


Digital Circuit Design

Digital Circuits – delabs

These circuits are based on CD40xx Chips and other. You can use 74HCT or any other series that is available. use one family for a particular project. These were used nearly two decades ago. Use it for learning, glue logic or to interface your uC designs to external devices. Do not make only Logic based designs like some below. It would be better to use a uC, CPLD or FPGA if you are building a complex gadget Basic Digital Circuits

LM331 is a Voltage-to-Frequency Converters and 74C926 is a 4 Digit Counter. The first part of the circuit converts the amplified DC analog value from a shunt to pulses. The Second counts the pulses and Displays it on a Seven segment LED display.

Digital Timers, Counters and Clocks

  • Sequential Timer CD40xx
  • Sequential Timer 7217
  • Six Digit preset counter CD4518
  • Analog timer CD4541
  • Quad Presettable Timers
  • Digital Comparator 74HC85
  • Sequential Timer/counter 7217 with RAM
  • CD4060 and CD4020 based long duration timer.
  • Digital Timer Clock With Preset using Thumbwheel switch.
  • 1 Hz or 1 pps crystal clock using CD4060 and 32768 Hz Crystal

Mixed and Interface Circuits

  • Optical Proximity Switch
  • Profile Controller
  • Toaster timer 555
  • Quad analog input switch logic
  • Optical switch for water tap using LM555 and LM567
  • Diff input DS8830 to TTL convertor
  • Phase lock loop using 4046
  • Am hour meter for battery chargers or electroplating equipment. 74C926

Mains Voltage Stabilizer Circuits

Mains Voltage Stabilizer Circuits

These circuits were drawn for a person in Africa. See the thread here… stabilizer circuit. They were not tested by me, but are quite close to a practical design.

Stabilizer Step up 230V AC 500VA

This circuit is a design i did, not tested by me as yet. It can Stabilize Mains voltage to around +/- 10% . It can be used for both 110V AC or 220V AC inputs with modifications. The Output is 220V AC. There is an overload, under voltage and over voltage trip circuit. With some tweaks and modifications it might work.

Solid-State Stabilizer Step up 110V AC

This circuit is a design concept, not tested by me and i did it just to explain some ideas. The circuit uses opto-coupler MOC3041 of Motorola and the Triac BTA-16-600 of ST as a solid state switch or relay. It also uses the LM324 quad opamp from National Semiconductor which is low power and single supply. As the MOC3041 switches the Triac at zero crossover there is no inter-winding short of transformer on crossover hopefully, the control circuit is designed in such a way that more than one triac will not be turned on at a time, i would like you to give feedback.

Temperature Measurement and Control

These are documents and circuits which will help learn Basic Temperature closed loop control, There are many ways to control temperature.

  • ON-OFF Hysteresis or Dead Band Control.
  • Proportional Control with Reset.
  • Full PID Control, Manual and Auto Tune.

The first one is an electronic emulation of Thermostat or Electro-Mechanical Controls. The second is a Time-Proportional like a slow PWM. The third is the complete adaptive control.

While the first is like a limit switch, the second works like a SMPS, the third PID takes into account the speed of the process and dynamic changes or disturbances of the system and compensates in real time.

Example – In a Oven, one batch may have 100 metal boxes to heat, the second batch may have 10 boxes, the door may be frequently opened and the mains power (heater) may be fluctuating. A system that is able to adapt to these changes, without much readjustments is the objective of an ideal process control. The Accuracy and the Energy efficiency being the most important.

Process control Application notes

  • Temperature control in plastic injection molding
  • Cooling Temperature Control
  • Capacitor Temperature Monitor