Hot answers tagged

11

Yes, it's completely normal. Often a fixed voltage (for full scale input) is presented to the measuring circuitry (the "burden voltage") so the resistance of the ammeter decreases (more or less) linearly with the scale. In other words a 20mA range might look like 10\$\Omega\$ (200mV burden), but a 20A (called a 10A) range would be more like 10m\$\Omega\$. ...


10

Okay. Lots of problems. This mostly comes from just being slightly ignorant about symbols and libraries and pin assignments in LTSpice. It's actually pretty easy, once someone clues you in. I started by downloading the ZIP file you mentioned, probably following the exact same process you did. I unzipped it and loaded the .LIB file into NOTEPAD to check it ...


10

From a professional point of view, this is a critical problem. Missing termination will cause energy bouncing back at the end which isn't terminated. This could lead to strange random noise on the line, such as for example transients or random pulses that seem like ok binary pulses, but with wrong voltage levels etc. CAN Hi and Lo don't necessarily behave ...


10

There are two issues here. It is true that for the kind of DAC you constructed: $$V_{MAX} = \frac{2^N-1}{2^N}\times V_{REF}$$ where \$N=8\$ and \$V_{REF} = 5.000V\$ in your case. So you will never get exactly 5V out...the difference is always the voltage equal to a change in the LSB, which is also called the resolution of the converter. The other issue is ...


9

Apparently you are asking about "ECN", Electrochemical Noise, which is the source of RMS noise from Li-Ion primary cells, and all other chemistries. Quick Google search and some browsing of search results leads to the following scholarly article, "A Method for Voltage Noise Measurement and Its Application to Primary Batteries". They did several ...


9

Don't use a comma as a decimal separator (e.g. 0,75). SPICE was born in the US and typically expects you to use a period instead.


7

RS-485 and RS-232 a electrical-only standards. The same data encoding scheme is usually used on both. The difference is that RS-232 uses a single wire for the signal with levels below -5 V and above +5 V, while RS-485 uses a differential pair with 0-5 V levels. RS-485 is also intended to be multi-drop whereas RS-232 is point to point. You can chose to ...


6

This is how I handle queries, and I find it to be pretty effective. In your PCB window, right click on the component you want to identify with a query and right click and and select "Find similiar objects". This will allow you to narrow down what you are looking for and if you select "Create Expression" at the bottom, it will create an expression in the ...


6

There's green and then there's other green. This is why in engineering we use numbers instead of vague words. It is best to specify the actual wavelength. Most common "green" LEDs are on the yellow end of what most people consider green. These do have about 2.1 V drop at reasonable currents. This type is the cheap and common "green" variety. This ...


6

DAC output voltage accuracy can be estimated by looking at the data sheet and the output error limits: - Then you need to understand what terms like INL mean: - The graph above shows INL (integral non-linearity). Basically, it means that the DAC output could have to +/- 14.5 least significant bits of error from the ideal straight line. Given your DAC is 12 ...


6

If you build a current mirror with resistors of different values in the emitters, the output current (in a first order approximation) will be the input current multiplied by the resistor ratio. Your ampmeters are acting like emitter resistors. Each range will have a different value of burden resistor, so what you see is not surprising. You should put the ...


6

Well you define ext0 but try to use ex0. No wonder linking fails.


6

It must be a per cent mille (milli per cent) or 10⁻⁵. I have no idea why TI decided to use such an obscure unit in a data sheet. It is occasionally used in other fields of engineering, but I have never seen it used in electronics.


5

Analysis with a cheap USB logic analyzer sampling at 16MHz showed that occasionally there appeared to be only 7 clock cycles grouped together. From the hardware VHDL, I know this to be impossible - once a byte transfer is started, it will exchange bits on the following 8 clocks. I theorized that there was noise on the SCLK signal, causing a clock that was ...


5

Basically for compatibility with everything else, you should always lay the pins on your schematic symbol on a 0.1" grid. Either set the grid in the symbol editor to be 2.54mm or set it to be 0.1". If you need to make a metric footprint you can do so, use whatever grid you want to in the package editor. The packages don't appear in the schematic so you ...


5

I made a custom library for a 1x3 header with 5mm pitch on Cadsoft Eagle. Since I had to make the pins in metric, I'm having an issue now connected to the 0.1 inch grid that the rest of my schematic is in. This makes no sense. The physical pins in the package need to be what the real connector has, but that has no bearing whatsoever on how they must be ...


5

Suffixes in LTspice are not case sensitive, so your switch's off resistance Roff=1M is actually 1 milliohm not 1 Megohm. Change it to Roff=1Meg and it will work. Without a switch you get several thousand Amps because the initial conditions are calculated at DC and inductors are considered to be short circuits. The inductor in your circuit has close to 150V ...


5

As Dave says, not everything the DRC flags is an actual error. It's up to you to understand your design and decide what's really an error. What I'll add is the way to fix it: Make a copy of the optocoupler part in your own library, and change the pin properties to reflect how you'll use the part. To minimize DRC checking, you can set the pin type to "...


5

If you drew sparks with only a single probe, it suggests that you accidentally shorted across neutral to hot somewhere on the outlet. Studying and understanding the manual and the limits of the meter would likely help you to avoid such mishaps. (Or even worse such as fire or electrocution.) Any kind of measurement of mains power should use considerable ...


5

Most likely your file was corrupted, either during save, or a crash. In your case it looks like you corrupted it when you renamed it. Fortunately Eagle makes periodic backups of your files, and also a backup in the event of a crash. These will be files with the same name as your board file, but with an extension of .b## (crash backup) or .b#1/.b#2/etc. (...


5

If you have a linear circuit where Vout = f(Vin) and f(0) is ideally 0, it's easy, just null the input offset with 0V applied and apply something close to full scale and adjust the gain. No iterations required. For more complex situations where f is nonlinear and/or f(0) is not zero you may need to adjust the gain and offset both before and after the ...


5

The problem here is that you are designing code for synthesis without really understanding what that means. Synthesis generates hardware to implement your design : think about the implications of a loop whose range is not constant : it implies that, as you change the loop limits, hardware magically appears or disappears to implement that change. Ain't ...


5

Possibility 1: You mixed up the pins on your transistor and didn't hook it up right. Not every transistor has its emitter, base, and collector pins in the same order. Even different packages of the 2N2222 might have different pin order. Possibility 2: you blew up your LED. If this circuit works, the base of the transistor is at about 2.5 V. Then the current ...


5

Single-event upsets (SEU) at sea level tend to be caused either by radioactive contaminants in the IC manufacturing materials (particularly the metals) generating alpha particles or by high-energy neutrons (caused by cosmic rays in the atmosphere) ionizing atoms in the silicon itself. Over the years, manufacturers have greatly reduced the threat caused by ...


4

CAN bus should have at least TWO active nodes. CAN Transmitter considers a transmission successful only if it gets ACK. When you configure a node in "Listen Only Mode", it recieves data but doesn't Acknowledge it. As there is no other node on bus, Transmitter doesn't get any ACK and hence Error. Try connecting one more active node on bus and do same ...


4

As Martin says, lack of proper terminators can certainly be a problem. However, R-C oscillators are generally not accurate enough for CAN. Usually you need less than 1% mismatch, which would imply .5% accuracy at each end, which the internal oscilators of these PICs isn't going to give you. Try with a crystal driving each PIC and see if you still have ...


4

That error indicates that the target device isn't powered. Check that the supply to the Vdd pin is present. The use of a voltage divider is probably the cause of the problem. Use a proper regulator. The Vdd pin should be decoupled.


4

This won't answer the question asked originally but it might help other people landing here: I used an arduino (and later bought a USBasp clone) to program an ATtiny85. This worked pretty well for a fair amount of time until suddenly, without any obvious reason, I kept getting wrong device signatures from my Attiny: avrdude: Device signature = 0x1e010b ...


4

I figured out how to assemble without error messages. The error messages you see are caused by the fact that avr-as does not invoke the C-preprocessor and therefore the #include lines are read as regular comments. Create a file ledON.S and notice the CAPITAL S in the filename. The capital S indicates that the C-preprocessor must be invoked first. Create ...


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