# Tag Info

1

What you need is Logic level converter, you can acomplish that with one or two transistors BC547 like in the image : You can also check this thread. There is also this really interesting logic level shifter from sparkfun :

2

I presume you mean the L298 H bridge. It's generally a very poor choice compared to what is available nowadays. The basic problem with this (and the L293 and SN754410) is that as soon as you take any meaningful current from the output, the power transistors become inefficient and you might lose 3 volts per H-bridge when powering a 1A load. Look at page 3 on ...

0

I'm certainly no expert but I think this other answer about efficiency using linear and switched mode circuitry is closely related to what you are looking for. How can I efficiently drive an LED? I understand that in your question you explicitly don't care about efficiency per se. But the switched mode circuitry gives a consistent output regardless of ...

0

You've asked a number of very general questions, so my answers will necessarily be very general as well. If you have a specific example you'd like to discuss, add it to your question. With a HDL design how can one predict that the combinational logic between two registers shall be more than clock cycle and thus there is need to use the multi_cycle path ...

2

I realize that this is an old post, but I thought I'd answer just in case... This PIC, and all other PIC18's that I know of, have an internal oscillator block. There is no need for an external crystal, even if you didn't have the 32kHz output. The only time you would need to use an external XTAL or clock would be: 1) to synchronize multiple devices to the ...

1

First, you could ask the LED manufacturer to provide to you the same bin. I don't know about your particular LED, but often, when the LED model is meant for lighting, the manufacturer can provide LED that have the same electric and optical parameters. To be simple: The manufacturer sorts the LED. You can ask to have all your LED from the same "bin". They ...

4

There are two things to consider in trying to match the light output of multiple LEDs Controlling the current thru each LED. Compensating for light output variances between LEDs even when driven with the same current. The first is not that hard to guarantee electrically. The brute force way to ensure the same current thru all LEDs is to put them in ...

2

Couple of comments about the optical portion of your project: Both the electrical and optical portion of the project are important but you won't be able to achieve a homogenized optical output even with perfect drive electronics unless you worry about the optical portion of the design which in turn may constrain how you plan to build/drive the device. ...

4

The simple rule of thumb I use is that when you get beyond about 6:1 it's time to compare other options. You're at 14:1, so well beyond that. You could always use multiple stages or push that duty cycle down further by heroic measures to get higher ratios, but the approach does tend to run out of gas. You might want to have a look at Analog Devices ...

4

As of now, I only have access to resistors for help. If there is a strong reason NOT to use just resistors, let me know! (I'm not an EE). Strong reason. Wasted energy, fire hazard, and voltage will vary based on load. You are wasting (24V - 9V) * 0.5A = 7.5 Watts of energy in heat in those resistors! Horrible. A small switching regulator module will ...

2

It may be possible to use a multichannel driver with dot correction such as the TLC5940 and adjust the dot correction of each channel individually until each LED appears the same. The '5940 can sink up to 17V, and 120mA when VCC is above 3.6V.

2

You should worry more about optical part of your light source device. Your circuit will be pretty homogeneous. You can use resistors with 1% tolerance if you want more precision or buy more 5% resitors measure all of them and only pick resistors closest to 100 ohm.

2

Which is the best way to have the same brightness from all the LEDs without use a dangerous voltage? Best depends on how complex you get and how matched you need. A simple method for a one off project, is taking a bunch of leds, say 4 parallel strings of 4 in series with an appropriate resistor on each. Light them up, then move them around by hand to ...

2

Which is the best way to have the same brightness from all the LEDs? There are three options: - Accept the manufacturing differences in light intensity between LEDs in a batch you buy Use a light meter and calibrate/test each one on a precision current source and be prepared to throw away 50% that aren't "good enough" Put variable resistors in series ...

0

All circuit elements which are in parallel will experience the same potential difference across them. Now start with the LEDs, the LEDS which I am using currently (in a personal project) http://uk.rs-online.com/web/p/visible-leds/7134888/ have a "forward voltage" of around 4V and a absolute maximum current of 80mA per LED. I have added resistors in so that ...

2

Assuming your resistors are similar and your LEDs are well matched, the circuit that you have show will give equal brightness. However, because there are manufacturing differences between both the LEDs and the resistors, it won't quite be equal. You could do some voltage matching between LEDs to be the same. Basically, put an appropriate resistor in line ...

1

You are right for the 4 parallel connection. The the amount of rows, I'm not quite sure your calculus is right, though. 1G is 1'024*1'024*1'024, not 1'000'1000, but apart from that, you would use multiplexers. The first 11 lowest address lines would be pinned directly to all chips' address bus. Then, you link the data lines of all chip that contain the ...

-1

LT Spice has been mentioned more than once, and I'll add that not only is it free and of high performance, but the user base is unusually active and helpful. Others such as TINA are out there, but you won't find the degree of help if you need to figure out how to stick handle around tricky modelling issues (eg. using tanh as an approximation for functions ...

0

I've tried Quite universal circuit simulator QUCS it is open source, multi platform and very easy to use. Analysis types include S-parameter (including noise), AC (including noise), DC, Transient Analysis, Harmonic Balance (not yet finished), Digital simulation (VHDL and Verilog-HDL) and Parameter sweeps.

1

Precision resistors are fine - think about when you have to use amplifiers and ask yourself which is the easier application - example below: - An ADC, at the end of an amplifier chain is employed to measure the voltage from a thermocouple. The ADC might have an input range of 0 to 5V or 0 to 2.5V or +/-1V or several other standards. However, the ...

2

There is nothing unreliable about a voltage divider at those voltages, it is the standard method. The voltage regulators that maintain those voltages will have internal voltage dividers to compare the output voltage to a reference of less than 5V in almost all cases. You probably do not really need 'high precision' resistors-- the tolerance on power supply ...

2

I think any engineering design is handled top-down when you really look at the design process. This is not limited to digital electronics or even electronics at all. Design of analog circuits is no different. You start out with what a circuit needs to do, then you come up with a overall strategy to solve the problem, then keep on drilling down until you ...

0

To calculate the turn in primary winding = 3.2 x 5 = 16 cm2, here we need to select the EI core voltage factor, If using silicon EI core, then one turn will give you 7 voltage. If normal EI core using then one turn around 8 to 9 voltage will get, there fore to find the number of turns in primary winding for 230V = 16/7 = 2.28 Volt, then 2.28 x 230 Volt = 526 ...

0

I think I see your problem... You state that you had a 70 mH choke originally but then removed two turns to get down to the picture showing 40mH choke. I don't really think from your pictures and from your description of two turns changing the inductance that you have an inductance that large. If it's that enormous coil with electrical tape around it acting ...

1

Capacitor Discharge through Constant Current Source From the link, you can get the equation for constant current through a capacitor. This allows you to assume a worst case spec of 2 Amps for the entire 600uS. Assuming you can virtually fully charge the capacitor in the off time (15% duty cycle). $v(t)= \frac{1}{C}I t + v(0)$. \\$ C = \frac{It}{v(t) - ...

3

There are a few other constant current type regulators to consider: - This biases a transistor to have a certain voltage across the emitter resistor and this means the current in the collector to the load is pre-defined. Can be used with a LED as load - it works by the BJT cutting the voltage supply to the gate of the MOSFET when the current thru R2 ...

1

Linear regulators actually make for good constant current sources because of fairly high accuracy between the output voltage and ground. All you need is a resistor between output and ground to limit your current. $$I_{out} = \frac{V_{out}}{R_{out}}$$ I will refer you to this Maxim application note for a more thorough explanation.

3

Given the very large head-room you have available from your primary supply, you should be able to just use the 7805 in current regulator mode: simulate this circuit – Schematic created using CircuitLab This would accomodate a wider range of load resistors if you could swap the 7805 out for a chip with a lower reference voltage and lower ...

1

There's a nice free Windows 8.1 app for designing stripboard/perfboard/breadboard called DrawingBoard Pro available from the Windows Store.

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