555 (TLC555) Relay Driver Circuit

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					                   555 (TLC555) Relay Driver Circuit

Multiple integrated circuit topographies are undocumented features or functionality. He is
one of them. TLC555 open output (PIN 3) open-drain transistor load 100mA sink v. 1.28
(PIN 7) 100mA sink 1V is reset. To connect, it is permissible, because they do the same,
and potentially double the current features of the receiver of 200mA. It is the perfect
place for the 133mA the relay coil to do.
Income is also a Schmitt trigger, but better known positive making the transition without
papers under the name of a feature.

555 Relay Driver Schematic

Protoboard setup
Output current rating (pin 3): TLC555 vs. NE555

                 (Vcc = 15V)                        TLC555         NE555
Source current                                   10mA           200mA
Source mode saturation voltage                   Vcc-0.8V       Vcc-2.5V
Sink current                                     100mA          200mA
Sink mode saturation voltage                     1.28V          2.5V
At the same time, if you keep a higher current consumption is the 555 and the saturation
voltage is very small is, unfortunately without excessive voltage drop in the truck. Also
shows that there are many, like for example TTL TLC555 acquisition ability is much
smaller than the absorbing capacity. To drive a relay, but we are only interested in flow
This is a 40A automotive relay (contactor) that I selected for this application. Since its
coil current exceeds the TLC555 output sink current rating, it is a good candidate.
Manufacturer or part number is unknown.

      Contact rating: 40A (from memory)
      Coil resistance: 90Ω cold
      Coil current: 133mA
      Coil power: 1.6W
      Coil voltage: 12V
      Pickup voltage: 4.8V cold
      Dropout voltage: 2.1V cold
      Operate time: 4.5mS

What is the difference between a relay and contactor is? There is no clear distinction
between say the current level and/or the application - for me, it is something for 20A
relay signalling device. What does it cost 40 or more, or the power of applications is also
a subcontractor.

Schmitt trigger input

Input (pin 2) and limit the value of the input (6-pin) pins are connected - it's more to do.
12V, the upper bound is smaller than the 8V and 4. Two levels of voltage, which is not
nearly as Schmitt trigger. This can be directly attributable to the 4000series that CMOS
logic, which also works with 12V.
To compatible with TTL logic levels the two resistors in the schema to add. It loads the
internal divider, the voltage will be lower. Calculated in accordance with the
approximately 1.4 and 2.8 V.
Testing the performance

      Output saturation voltage:
          o 0.617V @ 133mA
          o 1.043V @ 200mA
      TTL high level threshold: 3.0V
      TTL low level threshold: 1.6V

How about the bipolar 555 and other variants?

The standard 555 saturates poorly (2.5V) at 200mA and its reset line (pin 7) is not
specified above 15mA, so it is not recommended. The intersil 7555 is a very low power
device, so that is not recommended either.

For the future

      Assorted relay driver circuits.
      555 Voltage doubler relay driver circuit.
      Relay economy circuits.

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Description: 555 (TLC555) Relay Driver Circuit