New answers tagged

4

That circuit is not very good for driving the LED. In fact it is very likely to damage it and too slow to drive the LED with the required carrier frequency. As anyone can try to copy your design, you should fix the circuit as most likely people don't understand why the circuit works poorly or burns up LEDs. The poor range can be due to LED being already ...


-1

Increase the led current by paralleling two 2N2222 transistors. I did it in the past and it worked.


1

Let's talk mechanics first. The typical scale is usually just a platform with four load cells used as legs in the corners. The cells are summed up electrically to produce reasonably consistent result regardless of where on a platform you place a weight. But do you really need four load cells? Not really. You can come up with mechanical arrangement where a ...


0

I got random shutdowns and reboots when powering a Pi Zero directly from an ESC. I don't have the ESC specs any more, but it should have had enough power. So in my experience, go for a separate regulator.


0

I see other people are not liking the lack of power switch too. I just got into raspberry pi and noticed it. I wrote this schematic to solve my own issue. Too bad the guys on that site don't have a good forum to post this schematic. I would suggest a variance of this schematic below, but add a 5V relay on the USB 2.0/3.0 port 5V pin in place where I have a ...


1

simulate this circuit – Schematic created using CircuitLab I would use a TIP122 transistor, with an 220 Ω - 1 kΩ basis resistor with a general-purpose diode (1N4148 or 1N4001) reversed biased for protection. As any overvoltage from the TIP122 would get shunted away from the Raspberry Pi's logic circuit. the tip122 saturates 100% because it is designed ...


0

There are two 5V. TP 1-3 is the input 5V from the mini-usb power connector. The other 5V (the usb 2.0 /3.0 port power) is hardware controlled by the regulator and turns it on after it sends a power good logic to the cpu and receives a clock signal from the cpu. Pins 2&4 should be less than 1 ohm (continuity) between pins them and tp1, tp2, and tp3 ...


1

Sounds like a fun project! You are right that it's a good idea to not drive the LEDs directly from the GPIO pins of the CPU. Yes, a ULN2803 works as 8 separate controllable switches between respective output pin and ground. (Input high means output is shorted to ground, input low means output is floating.) The breadboard test you describe sounds like it ...


5

Ah, ULN2803 is a 8-channel (low side switching) sink driver, for common anode LEDs. For common cathode LEDs, you need the complement/mirror: UDN2981 (high side switching) 8-channel source drivers. The following schematic might help to tell the difference between high side and low side switching. Appendices Appendix A - 7-segment LED Circuit Design v0.1 ...


3

For CA or Common Anode (+) digit drivers you need high side drivers for digits and low side current limited drivers for segments. like Pch FET or PNP for the high side and NPN or Nch for the low side. The ULN series are Low side Darlingtons switches that rise 1.2V above ground. Common is often tied to V+ for flyback suppression of inductive loads, which ...


3

I don't see, and you don't mention a ground connection between the Pi and the protoboard. Without it, operation will be unpredictable. A standard TTL or CMOS shift register IC (as opposed to some power shift registers from TI), can barely drive an LED, and won't drive a solenoid. You need one driver transistor per solenoid. Your part draws 300 mA at 5 V, ...


6

Use either of the circuits below taken from this answer; just take the output from your shift register as an input to the MOSFET gate or BJT base to greatly increase the available solenoid current. Example from that answer using a BJT. The schematic calls out a Darlington transistor (effectively a two stage transistor); given that the solenoid requires ...


7

Use any power transistor ( BJT or Nch FET) as a low side switch, that can easily drive 300mA, which the CMOS SR cannot. Use a switch rated for low power dissipation (I^2R) or very low Ron on the low side plus a flyback diode from the Switch (drain or collector) to the opposite rail (Vbat) to continue the current but decaying to zero with the back EMF ...


2

No it is not suited. Raspberry Zero power specs recommend at least 1.2A supply for the Zero itself, plus whatever the relays and other circuitry uses. Besides that model is supposed to be soldered on PCB. It would not be very safe or professional to connect it in any other way than soldering it on a PCB.


1

Here is a buck converter circuit I quite often use. If you have the parts you can try building it. Edit: I have a typo in the design. L1 is 47uH, naturally not 47uF.


1

Yes, it's needed, usually you don't want to argue with datasheet suggestions, they are there to make the device perform according to what is promised. These devices consume current in gulps based on clock they operate at, and any wiring you add will make voltage noise higher at the chips unless capacitors are used. Besides, Raspberry Pi has a switch mode ...


3

VGA signal requires a pixel clock starting 25MHz (for 640x480, 60Hz refresh), or more depending on the desired resolution. A typical Arduino processor clock is up to about 20MHz (specifically Uno can be clocked up to 20MHz), so there is really no way it can generate such a signal without extra hardware. Sure one can go for any lower resolutions, but I doubt ...


2

No, an Arduino Uno can't display high-res photos on monitor.


4

I wrote a C implementation (see below) based on the pseudocode in Vladimir's answer. Works like a charm on my Pi Zero W, I'm using it to toggle the backlight of an LCD display by touching its bezel. I used a 1MΩ resistor, which takes ~20μs to charge when idle and 45-110μs when touching. It can even sense touch through the non-conductive coating on the bezel, ...


3

Having it shut on and off with the printer may be a bad idea- corrupted file systems and so on will likely haunt you unless you manually do an orderly shutdown every time. But you could use a DC-DC converter to get 5V from 24V for the Raspberry Pi. There may well not be enough excess capacity in the 3D printer power supply to provide an extra 15W or so. ...


0

Make sure you added a pull-up resistor on both the SDA and SCL lines to VCC. It's not certain whether the breakout contains some. Anything from 1 to 10k.


0

The first two leds were the problem. I tried everything, connect power and ground and move the signal cable around, trying in every position, even cutting the first led didn't fix it. I had to remove (cut off) the first two leds in order for it to work. Thank you


2

This is already said at least twice by others. Here's my version of the refrain: Signal needs 2 wires: The hot and the ground. You have several ground connections between the computer and the amp. The ground side signal current is distributed through all of them. The signal has no way to use the one and only wanted wire. Unfortunately also the computer ...


3

My best guess is this: - The DC-DC converter is producing common mode noise on its output power feed to the RaPi. That CM noise will be referenced to 0 volts on the amplifier power port and, the amplifier is unable to cope with that CM noise applied to its differential inputs. To prove this, if you grab hold of an audio transformer and feed the RaPi signal ...


2

If you use a PWM to output an analog value, its high level is the CPU's power supply voltage, and its low voltage is the CPU's ground. The former will fluctuate according to CPU power consumption and voltage regulator transient response. It is not possible to keep a voltage exactly constant on a load that draws randomly variable current. When the Pi outputs ...


0

My youngest garage door opener dates back to the 80's, so things might be different now. But back in my day ... Except for the motor, the control system in an opener runs on 24-28 Vac relays. The button closure connects the relay coil to the 28 V source, and one set of the relay contacts keeps the relay closed after you release the button. When the door ...


0

When the button is pressed, it allows electricity to flow through it, between its two connections. You can wire the relay's N.O. and C. (not N.C.) connections in parallel with the button (i.e. wire one to each terminal of the button). It doesn't matter which one goes to which wire on the button. When the relay is activated, electricity can flow between N.O. ...


0

After some simulation an answer i have worked out using an CD4572UB, an SN74LV123A and the 74LVC1G07 from the original circuit as a follows simulate this circuit – Schematic created using CircuitLab P_GOOD is active high nRTC_INT is active low (an interrupt) RUN_PG is active high nRESET is active low (pulls GLOBAL_EN via low 74LVC1G07 open drain ...


1

Expanding on KD9PDP's answer. If the 3.3V from the RPi is noisy, you can improve the filter by adding a series resistor, electret mics don't draw much current. You may need to experiment with the resistor values. If you have noise on the ground wires, that is harder to fix. If you can float your RPi, connect the mic circuit ground to one point at the RPi. ...


2

I finally figured this movement out, it requires a pulse every 30 seconds at 24 VDC, alternating polarity every pulse. Turns out it uses the same idea as Gent of Leicester, cheers for that nudge in the right direction henros! The Seikos however have an additional coil that can be used to drive the clock backwards, thereby making it easy to reverse the clock ...


1

The first step in eliminating noise is to identify the source. I think you did a good identifying the noise source in this example. If the static does not exist when you use the battery but does exist when you you the Pi's +3.3V and ground, then the noise is from the Pi's power pins (which is pretty common). Think about it as noise on both the + and - supply,...


0

I found this page very informative as it covers different boards: One of the images from learn.adafruit.com: The pin names of the IC are: driver DIN matches SIN in the datasheet driver CLK matches SCLK in the datasheet And the full GPIO of the Pi is this: from: Raspberry Pi GPIO


0

2N2222 VCE can go beyond 20V so this circuit should work, based on your intent. You can use which ever viable RPi pin you have for both the PWM output and the RPM input pins.


0

You have a relay module similar to if not exactly like this The basic components are an optocoupler a For input, a transistor for driving the relay, and a status led, flyback diode and passive parts like resistors. Of you measure the two pins marked vcc they are the same connection and so is both ground pins. IN + is the high side of the opto and IN - is ...


0

This is a 12V relay, so you need a 12V power source to operate it. I'm not sure if your raspberry pi GPIO will be able to operate it even if you provide 12V to VCC. You may want to get 5V relays like this that are designed for the raspberry pi.


1

I also suspect that the voltage that reaches the sensors are not the same. The wires are long, there will be voltage drop. Make sure the contact is good. You can try and swap the connectors of the two thermometers and see if something changes.


2

Unfortunately, fake DS18B20 devices are well known to be (a) inaccurate, and (b) have varying readings even in a stable environment. The chances of your devices from eBay being fake, is approximately 100%. This graph, taken from this answer on the earlier question: "Which one of these DS18B20 temperature sensors is fake?" shows the problem. The one ...


1

According to the datasheet this is the typical performance curve: Maybe they are not original, or maybe you have one of the "lucky" 0.27% ones which went beyond the 3-sigma interval.


0

Solid state relays is what I would use to switch the 48V@100A


0

Its partly a design problem due to the lack of power blocking diodes not installed in series with the USB ports. But there is ways around this issue. When the Pi is connected to a usb device that applies power back to the pi and the pi's power cord is disconnected, the 5Vsys and Sys2 pins receive a logic hi, but the 3.3V is not present because the power cord ...


0

Like stated above, the i/o has pretty "good" esd protection. These, like other computers are prone to malfunctioning by RFI and a metal case will always be recommended for someone building a computer, and is why the standard computer cases still have metal motherboard trays. External connectors to i/o that are connected while running, I would use ...


0

The green light is Read/Write activity from your storage device (sd card, hhd etc) it has no reference to any GPIO activity. As for your 5V power, its is as good as what you bought to power the PI, so current capacity are really limited to the USB3 power port, the pcb lands up to the header. I wold say at the most power it could handle without board damage ...


1

There are many ways to do this, but the easiest way would be using a 74HCT14 and chaining two for the proper logic. I would use the 5V rail in the Pi for this to power it. I would also put a 100 ohm resistor in series from the Pi's GPIO pin to the 74HCT14 just for protection in case the 74HCT14 fails.


3

The normal connections for this device are: CSn - use a CSn from the SPI interface. This is provided on your host. Also recommend a pull-up on this pin to deal with the host reset / startup case before the kernel has configured the pin. You must connect this pin to a valid CSn signal. SCK - clock from the SPI interface D0 / MOSI - 1-bit data input to flash ...


1

I note your pins SCK and MOSI are the other way around from the adafruit examples which say dots = dotstar.DotStar(board.SCK, board.MOSI, 30, brightness=0.2) So it's possible that although you're using the SPI pins, the clock and data can't take advantage of the hardware transceiver. You might be forcing it to send the bits in software, which in Python, won'...


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