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Thanks eTech , The N MOSFET I have easy access to is the IRLML6244 which has vgs(th) of 0.9V, this should suffice.
I have simulated the following circuit, which seems to be working and will test later today:
On further investigation it seems my suggestion to use depletion mode P channel MOSFETs in not practical as they seem to be not readily available and are considered speciality devices. :(
We can scratch that idea
Thanks for the response, Due to some physical limitations on the design i.e. the microcontroller and power indicator led being located on different PCB's linked via connector, we do not have 3v3 bus on the board with the power indicator led. So we need to power it from the 5V rail. Its also...
Good Day,
I am struggling with what I thought was a simple enough circuit. Would like to know what the correct way would be to handle this situation. I have two voltage rails, 5V supply (V_BUS) and 3v3 (from a LDL1117S33R buck). I am trying to get a LED to turn on when the 5V supply is...
I bought a bunch of "self adhesive standoffs" absolutely love them for populating a empty enclosure. pop them into your boards mounting holes, peel the backing and stick. They stick surprisingly well... had to fight with a few to get them to unstick...
Thank you Diver300, I've been searching the web and only came across recommendations for snubbers and chokes. Now that you've pointed me in the right direction I see that an NTC is exactly what I need.
I managed to source locally the following NTC (Datasheet) which is a 30 Ohm 5 Amp Inrush NTC...
Good Day,
I am hoping someone can point me in the right direction.
I needed to run four AC "high" power electronic ballasts for fluorescent tube lights. Each electronic ballast is rated 75W and globe is matched at 75W. The four globes total 300W. All ballasts are wired in parallel. (i.e. all...
Good Day,
Im trying to implement an "intercom" system using microcontrollers for a PoC application. We have 1 common wire line biased at 9V and two or more intercoms each with a microcontroller based on Arduino. Each TX/RX intercom device can listen and talk on the common line. Im using a non...
To close this thread, rjenkinsgb was spot on, I managed to wire all GND's and Earth together after swapping out the 5V SMPS with a new unit. I think running it with offset voltages must have caused an internal fault on my original unit.
Thank for the help
Good Day,
If an embedded system has one I2S bus with pins CLK, WS, SDO and SDI. Is it possible to connect two I2S IC devices? One being a DAC and one being an ADC? Where they share CLK, WS but the ADC will wired to SDI and DAC to SDO.
I have a device that uses a PCM5102 DAC and only the...
Thanks for the quick reply. I've been scratching my head for sometime with this.
I have actually tried disconnecting the Raspberry Pi i.e. No device on the 5V line. even in this state joining (E) to (GNDa) shuts-off the +5V SMPS. :(
Edit- With GNDa, GNDb and Earth wired together I still find...
Good Day,
Im struggling with a weird SMPS issue.
I have the following component connection layout, includes a AC->DC 24V SMPS that feeds a DC-DC 5V SMPS:
My 5V SMPS "shuts off" as soon as I plug in the 24V supply to the Modem, I believe the issue is that the Modem internally is tying GNDa...
Hi All,
I am trying to integrate SBC (RPi) to a specific door bell intercom system. I have opened and tried to understand how the intercom works and can share the following circuit information:
The indoor unit (that contains the headset) is powered by AC which is stepped down and rectified to...
Found it!
The "helicopter/ticking" noise is being induced by the WiFi of the RPi. If i switch of the WiFi interface using:
sudo ifdown wlan0
The noise stops.
Still unsuccessful with shielding against this... I must say RF is black magic.
Thanks guys, So yes I am convinced that the Raspberry Pi is somehow emitting this noise. Also the fact that the noise "sound" changes with computing load that the pi is handling.
dr pepper , would you mind sharing a rough schematic of a suitable choke circuit? I will also try to find an old...
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