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# Economiser Circuit for Contactor

#### Leoscar2000

##### Newbie
Hey guys, I've been assigned a little project for an extra-cirricular activity though I'm not sure where to start. It involves making an economiser circuit for a contactor to make it more efficient. I'm not sure where to start, I think a schametic might help. Any suggestions?

### Objectives​

• Design a circuit for an efficient economizer that will operate between 9-32V.
• Peak and hold
• Provide a constant current source.
• Use Digikey, LCSC, and/or Mouser, electronics distributors for parts.
• The PCB must fit around the contactor in a small, confined space. It must have a very small form factor.
• Have the inputs only be power and ground for minimal wiring.
• Calculate the power consumption of the circuit.

### Contactors​

Contactor 1: 2272229-1

• Minimum 550ma pull in and 170ma hold MINIMUM, may vary from unit to unit
Contactor 2: 2138622-1

• Minimum 333ma pull in and 160ma hold, these are minimums and may vary from unit to unit
Both contactors:

• 25ms pull in time minimum
• Operating voltage for input circuit is 9-32v, 9v min is contactor maximum pull in voltage
• 32v is highest expected supply voltage
• Must regulate current - not just PWM

Is the device similar to a relay? The economizing is probably to increase its useful lifetime. One factor is whether you have DC going through the contacts, or AC. At the moment of making or breaking contact, you want to do so when AC volts=0 and current=0. This minimizes tendency to arc. Arcing eats up contacts.

What about DC? Are you supposed to build a circuit that starts at zero current, then make relay contact, then increase current to the spec amount?

Treat it like a solenoid relay aka contactor with a timer with a 2 level CC limiter driver.

Search for a SMPS buck design with a variable output to regulate current that operates with the rated Vin and Iout such as a hysteretic buck current regulator.

LT1028 is good low noise but poor for Vin CM range and output swing.