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Build a constant current circuit – I am building a circuit which will provide me a constant current-to-end application. input voltage: 60v, Constant current will be 300mA. Ideas? Read more

Sinusoïdal power inverter – I’m  thinking of building a sinusoidal power inverter (around 3000 W) for my home. I am 100% on solar energy.
The principle seems simple ;
First stage to produce a sinus wave form (60Hz) ==>> Amplifier to get 12V (and much amps) ==> Transformer 12V/110V
Is it really so simple? Why are the comments on internet so weird about building it. Why are the prices so high? Read more

Overload voltage of 1206 resistor and damage to resistor – The 1206 SMD resistors in the attached R/Zener regulator will both have a voltage of some 350V across them during mains transients. Will they be able to survive this? After all, the overload voltage for a 1206 resistor is 400V. We could add a SMCJ440A TVS, but these suffer a clamp voltage rise up to 713V during their transient clamping. Read more

Sinewave inverter under load – I have finished the design and implementation for a pure sinewave inverter. The first stage uses a push-pull to convert 12 V DC to 310 V DC with feedback, so there is no problem with the load on the DC side. The range measures between 35 to 315. With a full- bridge MOSFET using a PIC MCU as a signal, under 100 W load, I get a pure sine wave form on the AC side of ~ 220W. But when I add more load the signal converts to triangle, not sine. Read more

12 V inverter circuit need clarification -What will be the output if I connect a capacitor in a simple 12 V inverter circuit at the output terminal of the primary winding transformer? Read more

Charge lead acid battery – I have two 12 V 2Ah lead acid battery’s (YUASA NP2-12). These are serially wired to give 24 V 2Ah. I am looking for a suitable charger or a schematic for such a charger. Read more

Sinusoidal control of BLDC motor – I am referring to the following document which controls the PMSM motor using sinusoidal signal. I measure the current speed using the Hall sensors and read the set reference speed and adjust the amplitude of the sine signal. I calculate the frequency of the signal based on the Hall signal and generate the sine wave of the same frequency by switching the legs. I can generate the sine wave using a lookup table but why is the document referring to space vector PWM? What exactly is space vector PWM? Read more

Buck converter burns if I plug an already opened power supply –  I’ve designed a buck converter circuit using L7981A exactly as it is described in its datasheet. It normally works fine. If I first plug the connector, then open the power supply, it works perfectly fine. However, if I first open the power supply, then plug the connector, it burns (i.e. the input terminal of the buck IC becomes short). Circuit draws around 100mA. My schematic is below. Read more

Understanding Op Amp parameters – I want to understand the curve shown in this op amp datasheet.

1) Open Loop frequency response
2) Large signal frequency response
3) GBWP VS Temperature
4) Output voltage vs Output current??

I am thinking about the basic LM358 operational amplifiers Read more

Li-ion Battery Life Time prediction + storage – We use Li-ion batteries on our various handheld instruments. One of the batteries we use is of prismatic type 630mAh (4.2V max). We did some tests on a sample of 20 batteries to predict their life-time in the instrument. Tests were done on a test jig that continuously charged/discharged the batteries in a controlled manner.  The question I have is that do you think if our test is an authentic way of predicting the battery life OR are there any other factors we need to consider that would affect the Li-ion battery life?

Secondly, we have a bulk of these batteries that have been sitting in storage for a couple of years without any preconditioning OR Charge/Discharge/Charge. Recently we noticed some of the batteries swelling in the storage (No external short circuits). Is there a recommended method of storing the Li-ion batteries (i.e., should they be charged to any level before storing? and do they need to be regularly charged? Read more