8
votes
Accepted
How is switching of measurement ranges in instruments, like oscilloscopes, realized nowadays?
Small sealed telecom style relays are frequently used. They have many advantages over solid-state switching (low leakage, low 'on' resistance, low capacitance, high voltage capability) and are ...
4
votes
Accepted
Driving relay without a control Fet: Back EMF consideration when control side is Grounded
The GND will stay 0 V unless you have multiple connections that can cause a high drop therefore a non-zero (substantial) potential difference across all the 0V connections.
The relay coil is an ...
- 38.1k
4
votes
How is switching of measurement ranges in instruments, like oscilloscopes, realized nowadays?
Reed Relays are still pretty good - if not the best - signal switches. With an extremely good ratio of Off/On impedance, they are much better than FET switches, as far as I know.
Their drawback is ...
- 22.8k
3
votes
Correct schematic to drive 12 V relay?
Neither one is correct. The coil is pins 1 & 4. The diode is correct so either the collector goes to 1 and Vcc to 4 or the reverse. Based on the diagram in the schematic symbol you have and ...
2
votes
Driving relay without a control Fet: Back EMF consideration when control side is Grounded
With high side switched relays the A1 terminal (relay positive) will go negative on power off due to the inductance. Current remains flowing until energy is dissipated.
So in your case A+ will go down ...
- 23.6k
1
vote
Driving relay without a control Fet: Back EMF consideration when control side is Grounded
I think I got it. The point where the coil connects to the GND might not be able to rise to 24V, but since the "24V REL" net will drop to 0V and keep decreasing, once it reaches -25V, the D4 ...
- 3,490
1
vote
Potential Free contact for VFD using Relay
This relay output can be configured for a variety of functions. You choose the function by setting parameter A055 in the VFD.
To be clear, this is one output relay, with two contacts: one Normally-...
- 680
1
vote
Potential Free contact for VFD using Relay
These relays can be used for primitive fault signaling in basic applications.
There are often two relays, alarm and fault. Alarm is often reprogrammable.
Many industrial devices in a machine have such ...
- 23.6k
1
vote
Accepted
Potential Free contact for VFD using Relay
But what if Emergency switch (NC) is pressed ? How will VFD know what happened?
For industrial control systems complying with international safety standards there are two common ways to stop the ...
- 178k
1
vote
Can a switch be put on the collector side of npn BC547 rather than the base side?
The two circuits are not the same. They achieve the same function in different ways.
A significant difference between the two circuits is that in the right circuit, both the transistor and the switch ...
- 22k
1
vote
How should I control a 24VDC solenoid using 12VDC relay and separate power supplies?
Relay contacts are voltage-agnostic within their ratings.
You can use a 12V-coil relay to switch a 6V, 12V or 24V solenoid.
However if the same contacts on one relay are required to switch multiple ...
1
vote
Determine adequate speed of flyback diode for a relay
Diode speed is essentially irrelevant: diodes are normally rated in terms of reverse recovery, but there's no hard off-switching in this application. With such high inductance in the coil, recovery ...
- 43.5k
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