Tuesday, February 17, 2015

Single Chip dual power supply

message: Hello, I want to know the single IC which can provide Both + V and -V from a single +Vin supply.. I need this for my dual supply opamp.Reply me as soon as possible. -  Thank u.

Mail from KM

There were chips, but now obsolete as most use a smps circuits. you can try this RS232C Level Converter it has -10 and +10 that can power low-power cmos opamps and chips.

or use LM7912 and LM7812l you will need two chips, there was a LM326 but not now. See Linear Regulated Dual Polarity Power Supply

When a Inverting Opamp Configuration is at a steady state, we say the Inverting Input is at a Virtual Ground. That means it is at 0V w.r.t to the dual power supply ground, but it cannot drive or draw any current. It is at a high impedance, but still at 0V. When you buffer this 0 V, you get a low signal ground for a opamp supply. Opamp generates Virtual Ground. See this a Isolated dual power supply from 5V

Dual Polarity Power Supply


I am very happy to see ur reply.I am appreciating ur job. Ok.. Ur information is most useful for me.. We ill meet with another problem.. Thank u..

Mail from KM

Friday, February 13, 2015

Some Cyclic Timer Ideas

A product spec and need from my email archive. This indicates how clarity in customer specs can help him get a working solution with less wastage of time and money.

Electronic design assistance

I am seeking assistance from someone that would assist me in designing a custom circuit for a prototype that I am working on. I would be willing to work out a mutually lucrative contract with someone who wanted to get involved with this project.

General Circuit description

Cyclic Timer

Circuit components:

  • Tank filled with liquid.
  • Fluid hose to pump
  • Fault switch or Low level float consisting of a magnetic float encased around a tube with a no/nc reed switch.
  • Liquid 12vdc @ 5a pump
  • Trigger momentary switch to activate cycle.
  • Reset Switch.

Circuit requirements

When momentary switch(3) closes for 2 seconds, pump(2) will activate (ON) for an adjustable time from 2-3 seconds. After pump(2) has activated an adjustable timed 10-60 minute countdown of the pump (off) will begin. Any additional signals from momentary switch(3)will not interrupt this cycle. If when cycle is complete a switch closure from momentary switch(3) still exists the cycle will repeat. If at any time circuit receives a signal (NC/NO) from fault switch(1-B) cycle will be immediately shut down and not restart until manual reset switch(4) is pressed.

Notes: 3. Momentary switch to activate cycle could be in the form at current of an ultrasonic movement detector as seen here.

I have not tested this switch yet to insure that it will perform the necessary detection capabilities, so this may change if a more suitable device is located.

Notes:4 The reason for the manual reset button or circuit is that the float switch is very sensitive. The potential exists that when liquid level is low and pump activates, the amount of fluid that the pump draws to prime itself, may momentarily fool the float switch into thinking that tank has become empty. When pump shuts down and pump looses it's prime a small amount of fluid will back flow from pump back into tank causing the level to fool the fault switch into thinking it has an acceptable level. I want to avoid a toggling effect that may be created when level gets into this level of liquid.

General Notes: I have found several cyclic timers that could possibly perform the above list of requirements.

Mail from RS

Standard Solution

Similar thing here two-stage-sequential-timer at  delabs Service Project Circuits


Sunday, February 08, 2015

Thermostat with digital display for PTC1000

Thermostat with digital display, I need a electronic thermostat with a 2 digit display... Do you have anything like that??

mail from EU

can you explain how you plan to use it. then i can give you a suitable circuit. It it for a bakery oven or plastic injection moulding. do you want on-off control or proportional control. do you need a circuit and pcb or only circuit. do you want me to make a custom design for you.


Thank you very much for responding my e-mail! It´s really for may kitchen oven and I did put an on-off control but..really doesn´t work quit well so I thought in putting a proportional control or would like to have both, on-off and proportional, and see which works best.

I want to quot that it´s NOT FOR COMERCIAL USE. It´s only for only for my home. I was looking tru the internet but didnt find what I want. I would like a simple thermostat with a two digital readout probably made with OP-AMPS cause with microcontroller it´s quit difficult for me because I don´t have a programmer and, also, do not understand quit well how they work either.

I was thinking in the using of PTC 1000 (because I already have it, that´s why) or any PTC, NTC or pt 50 or pt100

I only need the circuit, no pcb. If you know a place on the internet where I can find something like that I would really appreciate it very much. As I said before, something simple no big thing, but I need it with a 2 (or 3 not important 3) digital readout so my wife can see the temperature in the oven. Thank you again for your help and time, thank you.

Reply of EU

Blind Dial Proportional Temperature Controller

Blind Dial Proportional Temperature Controller

See this blind proportional temperature controller, pdf here Analog Circuits and use the display temperature controller, display, pdf here Temperature Control Circuits on same page some digital indicators are there use them for display.

You could also try this High Reliability Thermostat, i found it very interesting, pretty simple.


Thank you AGAIN!! Thank you for your help and time. It´s just what I need!!! Thanks a lot!!

reply of EU