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227

An LED requires a minimum voltage before it will turn on at all. This voltage varies with the type of LED, but is typically in the neighborhood of 1.5V - 4.4V. Once this voltage is reached, current will increase very rapidly with voltage, limited only by the LED's small resistance. Consequently, any voltage much higher than this will result in a very huge ...


35

I would argue that there are fewer "gotcha's" with option A. I would recommend option A to people of unknown electronics skill because there's not a lot that can keep it from working. For option B to be viable, the following conditions must be true: \$V_{CC_{LED}}\$ must be equal to \$V_{CC_{CONTROL}}\$ \$V_{CC}\$ must be greater than \$V_{f_{LED}} + V_{BE}\...


25

Converting to a "24 V signal" is missing the point. The real problem is driving a 24 V relay from a 5 V digital signal. Fortunately, that is easy. Here is one way: You didn't say how much coil current the relay draws at 24 V, so I picked an example part I had in my system (Zettler AZ8-1CH-5DSE). Figure the B-E drop of Q1 is about 700 mV. This means ...


21

An even better variation on your option "B" is to put the LED in series with the collector, while leaving the resistor in series with the emitter. simulate this circuit – Schematic created using CircuitLab This turns the transistor into a controlled current sink, where the current is determined by the base voltage, minus VBE, across the resistor. The ...


20

You should always tie unused inputs to a valid logic level. That could be tied to GND or to the VDD voltage rail. Never leave unused inputs floating in that it can cause excessive power dissipation in that IC package and introduce extra noise into the voltage / GND rails. It is common practice to use a pullup or pulldown on the unused inputs on unused ...


18

Flicker is a result of too slow refresh. You need to refresh each segment at a few 100 Hz minimum. However, there are some tricks that can reduce apparent flicker while not actually doing faster refresh. The naive approach is to refresh the digits in order. But, if you alternate them a bit, the whole number will appear to flicker less. For example, do ...


17

The answer is at the end, but, just in case you are not familiar with the concept of MOS capacitor, I'll do a quick review. MOS Capacitor: The Gate of MOSFET transistor is essentially a capacitor. When you apply any voltage to this capacitor, it responds by accumulating an electrical charge: The charge accumulated on the Gate electrode is useless, but the ...


16

There is one other way, much less commonly seen. Good for one LED, very simple, you can throw anything from about 4v to 20v at it, and it happily gives the LED a fairly constant current. Blue is the input voltage, 20v to 4v. Green is the current to the LED, about 12mA. Red is the power dissipated by the JFET, datasheet here.


15

At some point in my life, I used to run the USB business for big semi company. The best result I remember was NEC SATA controller capable of pushing 320Mbps actual data throughput for mass storage, probably current sata drives are capable of this or slightly more. This was using BOT (some mass storage protocol runs on USB). I can give a technical detailed ...


15

The diodes in this application are not there to block current, but to allow a low-impedance path for the coils to discharge themselves through. If such a path is not provided, then when the coil's supply is stopped at each cycle, the stored magnetic energy must find a path for discharge. This results in the coil expressing an arbitrarily high reverse voltage ...


14

A microcontroller has a very low output current. You shouldn't drive directly more than an usual indicator LED with it. The motor draws a much higher current. Connecting directly will result in not working motor and destroying the microcontroller due to high currents. Drivers are not used only for motors. They are used for any device that usually draws ...


14

A LED/LCD display is constructed of multiple panels: 16x16, 64x64, etc depends on the supplier. These panels are mounted such to produce the 1920 x 1080 pixels Each panel will have its own interface IC and LED/LCD driver chipset like the tlc59283 How is each panel/module controlled? via a serial interface. If you look at a 320x240 panel such as this one ...


13

Assumption: LED Driver used is PDA012A-350S-R, from link provided in question. Assumption: A single LED is being driven, based on "flashing the LED about 3 times ..." The constant current driver is going into overload, due to being forced to dissipate power far over its design limits... From the datasheet of the LED, it has a forward voltage of 3.2 Volts. ...


13

Typically there are long skinny driver chips for row and column. They may be on the outside COF (Chip-On-Flex) or inside COG (Chip-On-Glass construction) the panel itself. Here's an HD TV panel from Dave Jones' blog showing the COF column drivers: Here you can find a datasheet for a Novatek driver chip showing the data interface for 384 outputs- 128 x 3 ...


13

Here is your circuit being discussed: R3 and R5 should not be getting "hot". Do the math. Even if Q1 were a perfect switch, there would only be 5 V across R3. (5 V)2(1 kΩ) = 25 mW. Unless this is a very tiny resistor, you wouldn't normally notice it getting warm. A 0805, for example, can usually dissipate about 150 mW safely in open air on a ...


13

Schematics like the one that you show should be regarded as simplified schematics - the actual implementation is likely more complex. Anything that is not specified in the tables, graphs or text --- generally with tolerances --- is not a useable design property. When reading the NUD3160 specification, I do find a property related to the value of the ...


12

I used valuable information from Telaclavo's answer to adjust mine. If you like his, don't forget to upvote him. If your duty cycle is 1/16 then you would have to give each LED 16x its nominal current to get the same average brightness. This will decrease your LEDs' life. High brightness LEDs can be PWM controlled at their nominal current at 1/16 duty ...


12

Option B requires the control signal to be raised to a higher voltage than the LED drop voltage plus the base/emitter drop voltage. If your control driver is able to operate at a higher voltage than the LED drop voltage plus the transistor base/emitter drop voltage, then Option B would be valid. Option A on the other hand can easily drive any LED drop ...


12

Try probing on the power supply rail. I bet you see those spikes on there. It'll be due to the lead length between your bench supply and the MOSFETs. Clearly you won't see it on the lower FET side because your scope is referenced to that rail but, if you probed back at the power supply I bet you would. Try a 1uF or 10uF ceramic across the power rails close ...


12

Figure 1. When Q1 is off both Q2 and Q3 are forward biased (green) and will turn on. The result will be shoot-through the two transistors (red). If the supply voltage doesn't collapse (1) will be at about 4.3 V, (2) at 2.5 V and (3) at 0.7 V. Ignoring R3 the current through Q2, R4, R5 and Q3 will be about \$ \frac {5 - 0.7=0.7}{2k} = 1.8 \ \text {mA} \$. I ...


12

Yes. All almost ICs need decoupling capacitors. Devices such as these '485 drivers especially need them due to the current surges the device experiences when switching the signal states to the low value termination resistors used on the bus lines.


11

This is an example of what happens, not intended to be overly realistic but to simply provide a visual. Actual effects can vary quite a bit depending on the circuit and where the parasitic capacitance is as well as how its interacting with other components. In short this is a heavily simplified example for illustration purposes only. Test Setup: A 1us ...


11

I'm (arguably) an international expert in this area. (Really, maybe :-)). One reason there are so many drivers is that applications vary widely and, also, the market is large and potentially lucrative. The answer will vary based on many parameters. I'll list a few, and if you can refine the question I and others can refine the answer. What country you are ...


11

It looks OK, but the resistors should go on the cathode side. With the resistors on the anode side your display will change in brightness depending on the number of LEDs which are on. A "1" will appear brighter than an "8". Also keep in mind that the TLC59213 is a registered device: you'll have to latch the data on the inputs to the actual driver with a ...


11

The datasheet says Low input voltage noise: 2.2 nV/√Hz. The parameter is really just input voltage noise, and they are saying that it's low to make the part sound more awesome. The noise is usually modelled as having a constant spectral density. Thus, the spectral density of noise power would be specified in \$\mathrm{W/Hz}\$. The higher the bandwidth (for ...


11

\$R_{\theta JA}\$ is one small part of the story. The main part of the story is \$R_{\theta JC}\$ (at 1.5 °C/W), because this is the junction-to-case thermal resistance and it adds to the heatsink thermal resistance to give the lowest (normally) path for heat. So, if the thermal resistance of the heatsink is (say) 6 °C/W then the total thermal resistance ...


10

Here is a collection of LED driver options you can play with. simulate this circuit – Schematic created using CircuitLab


10

With any CMOS logic IC, you MUST connect unused logic inputs to a known logic level. You may connect unused inputs to either High or Low, whicever is convenient (or whichever is necessary to make the part work as desired). An unconnected CMOS input may take on any level - if it sits at a "maybe" state, the input circuit will draw excessive current, and ...


10

Your understanding is correct. To break down the issues a bit more: Turning the MOSFET ON too fast can cause overshoot and ringing at the drain, hence the use of a low ohms resistor right at the gate. The ultra fast diode is to turn the MOSFET OFF faster than it turns ON, but the diode has internal resistance. What is bad is driving the gate with no ...


9

An H-Bridge contains 4 transistors. Often these are FETs. The gate of a FET is not as simple to drive as you might think, for two reasons: FET gates have some capacitance, which takes a little while to charge up to the threshold voltage. This in turn means the FET take a little to switch on. While the gate capacitor is charging up, the FET is only partially ...


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