New answers tagged

0 votes

ESP MCU, directly drive BT136

Answering (1) Can I use my NodeMCU's D2 pin (which is +3V) to drive BT136 directly without using any optocoupler? Yes you can, but it doesn’t mean you should. The circuit can be made to work, ...
user avatar
  • 536
0 votes

ESP MCU, directly drive BT136

can I use my NodeMCU's D2 pin (which is +3V) to drive BT136 directly without using any optocoupler? Yes. The DC GND (ESP's supply GND) should be connected to L (phase) or N (neutral), depending on ...
user avatar
3 votes

Is this single transistor interface good enough for this relay-control?

I have a different opinion and experience. The 100mAdc diode can certain handle 1A in 44 us = L/DCR=10m/227 and its higher resistance (10 ohm vs ; 1 ohm in a 1A diode) is actually a small benefit to ...
user avatar
4 votes

Is this single transistor interface good enough for this relay-control?

The 2N2222A is a metal can transistor (you may find some plastic transistors labeled 2N2222A by off-brands and online sellers but these should really be PN2222A). They are relatively expensive and ...
user avatar
  • 3,546
1 vote
Accepted

Is the same overcurrent relay used for both phase-to-phase faults and 3-phase faults?

Yes, phase-overcurrent. That said, you could use a negative sequence overcurrent for the ph-ph faults. Just learn how to coordinate it properly…not always simple as stacking curves.
user avatar
  • 3,275
2 votes

Control 12V relay by using Arduino

That should work, however it's possible you may have problems due to coil-contact coupling, depending on your load, the relay, and your layout and wiring. It's better to have a separate supply for the ...
user avatar
1 vote

Control 12V relay by using Arduino

Should work fine, I'm using FET instead of BJT but otherwise it's the same circuit. Just make sure that your diode is connected correctly (otherwise your transistor releases the magic smoke), your ...
user avatar
0 votes

Modifying RC controller to drive with Arduino

Messing with the receiver board itself is not worth it, get a dual H-bridge motor driver and you can completely replace it. Another solution is to have the arduino control 4 transistors (or as many as ...
user avatar
0 votes

Modifying RC controller to drive with Arduino

If there are 4 simple switches in the controller that should be replaced by something controlled by the arduino, an easy solution, without knowing the circuit in the controller, could be something as ...
user avatar
  • 6,103
1 vote
Accepted

Simplest solution to automatically turning off dash cam when ignition is off, but turn it on with button?

Here are a couple of options. Option A: It looks like the ignition wire acts as an inhibitor that keeps the camera from recording when it has 12v. You could use a switch (SPDT) to connect it to 12v ...
user avatar
  • 464
0 votes

Esp-01 and 3V3 relay module: unexpected resets (cause 4)

I added 104 and 106 capacitors to the reset pin and added a 3v3 pull-up resistor and the problem was almost completely solved. No more ESP crashes.
user avatar
0 votes

Motor voltage spike

The motor has considerable inductance (probably some ~mH), so its current cannot be set to zero instantly. An opposite voltage must be applied to cause the current to fall towards zero. This is ...
user avatar
0 votes

IR remote code amplifier

You don't even have to disconnect the existing LED -- it will have a ~ 2 V pulsing signal across it that you can use.
user avatar
  • 12.5k
1 vote

12V DC motor takes substantial amount of current when the direction is reversed

As explained by user287001, when you reverse the polarity of the motor, it acts as a generator, but its polarity is opposite to the power supply voltage, so it will draw a lot more current than even ...
user avatar
  • 57.5k
2 votes

12V DC motor takes substantial amount of current when the direction is reversed

Abruptly reversing a spinning DC motor can (and does) lead to big spikes of current, mechanical stress, and double voltage over the motor. To reverse the motors you should first ramp down the PWM to ...
user avatar
1 vote

12V DC motor takes substantial amount of current when the direction is reversed

The induced voltage in DC motors is the reason why the motor draws less current than the input voltage/coil resistance. The induced voltage is proportional to the r.p.m and it's like a voltage source ...
user avatar
  • 21.2k
1 vote

Relay system not always working

Here's a simple solution using only two SPDT toggle switches.
user avatar
  • 9,717
0 votes

Switchover delay in my UPS circuit

You're definitely making it harder than it is. The DPDT switch appears to have no good purpose. I gather you don't want the boost converter running while able to use AC power, so... I would re-wire ...
user avatar
1 vote
Accepted

How to connect a bistable valve?

The OP has confirmed that the valve automatically switches off power when it reaches the end of its travel, so while voltage may still be present it’s drawing no current and so there’s no need for an ...
user avatar
  • 5,350
4 votes
Accepted

Switchover delay in my UPS circuit

Sorry the first try didn't work. You should be aware that your approach is not much used for smallish systems. The basic problem is that, since you are starting to act when Vcc has actually dropped, ...
user avatar
1 vote

How to connect a bistable valve?

Here's how. An SPDT toggle switch is all that is required. At the end of opening / closing, the corresponding limit switch de-energises the motor.
user avatar
  • 9,717
0 votes

How to connect a bistable valve?

Solution is really simple: Feed the NO contact of each relay from the NC contact on the other relay. This way both relais interlock each other, and there will be open circuit if both are active at the ...
user avatar
  • 9,608
1 vote

How to connect a bistable valve?

Depending on the used bistable valve usually the internal control circuit has already an interlock and a limit switch. But if not the first solution is better however you can simply avoid adding a ...
user avatar
  • 2,567
2 votes

How to cut power to an embedded device without damaging it?

The device is battery powered; this means you have relatively low voltage DC power in mind for the shutoff. A relay is a bad choice here, because your battery power undoubtedly runs through voltage ...
user avatar
  • 6,612
0 votes
Accepted

Replacing button switching 1.3V with microcontroller

It's hard to say without knowing anything more than the voltage across the open switches. You could get some idea of the impedance of the inputs by putting a resistor between them and ground and ...
user avatar
  • 3,546
1 vote

Looking for advice on a 12V relay circuit with ESP32

The schematic looks functional. Maybe there's an issue with the PCB such as wrong footprint to schematic mapping. If you provide images of the PCB (and preferably a photo of the assembled PCB) we can ...
user avatar
2 votes

How to cut power to an embedded device without damaging it?

There is no special concern. You can control the power with any suitable relay or in many cases also with a transistor. The advantages of a relay are that it Just Works - it's easy to use. The ...
user avatar
  • 6,416
6 votes

How to cut power to an embedded device without damaging it?

Unless the device requires a UPS it should deal with unexpected power failures. If it’s poorly designed and file system corruption and such like is possible then all bets are off, you may need to ...
user avatar
0 votes
Accepted

Switch stuck in closed position

Switch contact welding is caused by high inrush current at switch-on. In power supplies the high inrush current is caused by charging capacitors. You would need to select a switch or a relay, from '...
user avatar
  • 9,717
0 votes

A question of a controlling PSU safely

Only half kidding but you could use a garbage disposal air controlled switch. They come in a variety of attractive finishes. Photo from Lowes.
user avatar
  • 6,540
0 votes

A question of a controlling PSU safely

Here's how. The fully-insulated toggle switch is mounted in a cutout made in the enclosure. The enclosure should also have a protective earth connection.
user avatar
  • 9,717
0 votes

A question of a controlling PSU safely

simulate this circuit – Schematic created using CircuitLab Figure 1. RLY1 inverts the logic of SW1. Relays are commonly available with 120 V and 230 V AC coils. ... when the switch is closed, ...
user avatar
  • 159k
1 vote

RC time delay circuit to trigger relay

As requested, this is a first pass at two alternate solutions. Neither have been simulated or built, and all component values are approximate, pending more information from the TS. Both circuits ...
user avatar
  • 12.6k
0 votes

RC time delay circuit to trigger relay

The following changes are to be carried out to make the circuit workable: The LED D2 is to be sourced directly from the 12 V supply (not through R2). The value of R2 is to be much lower than 400 Ω. ...
user avatar
  • 9,717
-4 votes

RC time delay circuit to trigger relay

You are describing a simple RC circuit as a control circuitry: simulate this circuit – Schematic created using CircuitLab This should work.The potentiometer allows you to select the time period ...
user avatar
1 vote

RC time delay circuit to trigger relay

Probably not good design practice to switch the 555's supply voltage, it'll probably give the poor little thing a headache! You could give the following circuit a whirl. At power-up and at rest the ...
user avatar
  • 4,940
2 votes

RC time delay circuit to trigger relay

One problem is that you are taking the power for the LED from after the 10K resistor R2, so it would never get enough current. That aside, as the rest of the circuit is in question as well, you could ...
user avatar
  • 3,546
0 votes

RC time delay circuit to trigger relay

simulate this circuit – Schematic created using CircuitLab This won't work because the coil resistance is 400 and that attenuates any chance of making a one (1) second timer as the 10k limits ...
user avatar
1 vote

Relay does not turn on when using a 2.5A 12V power supply

So does this mean I need to spec the power supply to the inrush current even though the inrush only lasts a few milliseconds? YES. The alternative is to have a battery and trickle charger that meets ...
user avatar
2 votes

Relay does not turn on when using a 2.5A 12V power supply

I guess your power supply has foldback protection behaviour. A short too high current peak drops the output voltage and it doesn't return before the load resistance has grown high enough. Constant ...
user avatar
  • 21.2k
2 votes

Using High Power Relays to Actuate an AC Motor

A motor is an inductive load. As the contacts open the inductor attempts to maintain current. Because of this the voltage momentarily increases. This effect causes arcing of the contacts. Arcing ...
user avatar
  • 6,831
0 votes

How can I control a firework igniter (e-match) with Arduino?

What level of safety do you require? In general, you can easily fire Pyro / Fireworks igniters using MOSFETs. You should provide a decent bulk storage capacitor to provide the energy required. You ...
user avatar
  • 22.6k
1 vote

How can I control a firework igniter (e-match) with Arduino?

A more powerful battery is surely not enough. An Arduino can supply only tens of milliamps where an e-match might draw a few amps. Just drive an Arduino relay module and let the output of the relay ...
user avatar
  • 111
2 votes

bi-directional motor using SPDT relay and diodes

This is how I would do it: - It requires two change-over relay contacts operating in tandem. You might also wish to apply back-emf quenching diodes too. Here's another version of the same circuit (...
user avatar
  • 379k
0 votes
Accepted

bi-directional motor using SPDT relay and diodes

Unfortunately this can't possibly work. The battery is basically shorted out on the bottom side of the motor. The only way something like it could possibly work is if you get the other side of the ...
user avatar
  • 6,416
2 votes

Can anyone help me with this delay problem in my UPS circuit?

It can be made much simpler. No relay needed. No buck needed. Only one diode. And a DPST switch :) simulate this circuit – Schematic created using CircuitLab Given that you're putting this ...
user avatar
0 votes

best 5v switch with 3.3v

MOSFETs switch "loadless" basicaly it has a tiny capasitor inside that if charged opens the MOSFET BJT(Bipolar Junktion Transistors) switches with a "load" basicaly if the Base to ...
user avatar
1 vote

Switch off 2 power supplies using a single switch in a feedback loop

One way to make this work is to split the LEDs to only the way one is powered off of the second battery. In this case, you can use the switched first battery to operate the relay, acting as the switch ...
user avatar
  • 7,095
3 votes

Can anyone help me with this delay problem in my UPS circuit?

See that buck converter which drives the relay to connect the battery to the boost converter? That converter has a certain hold-up time. When Vcc drops, the output of the buck converter does not drop ...
user avatar
1 vote

Switch off 2 power supplies using a single switch in a feedback loop

The lights look great! I have done similar things in my house. Is it possible to increase the voltage, if not ok. In my proposed solution the increase in voltage will reduce the current in the wire ...
user avatar
  • 2,553

Top 50 recent answers are included