# Construction Relay

#### Jimmie

Joined Mar 14, 2008
1
I want to make a simple relay. 12/24VDC to be opreated at currents exeeding 450 mA/160 mA,. The required size is diameter 11 mm Length about 26 mm. What dia coil to be used and the number of turns required. Can any body help me? Thanks
Jimmie

#### thingmaker3

Joined May 16, 2005
5,084
I've moved this into its own thread to avoid confusion discussing two similar, but distinct topics. The other thread http://forum.allaboutcircuits.com/showthread.php?t=10096 dealt with an existing relay as part of an existing circuit whereas this one deals with building a relay from scratch.

#### SgtWookie

Joined Jul 17, 2007
22,210
I want to make a simple relay.
Single pole, single throw, normally open? Or something else?

12/24VDC to be operated at currents exeeding 450 mA/160 mA.
The contacts, you mean? Or the coil?

The required size is diameter 11 mm Length about 26 mm.
Is that the maximum size in all directions, or your coil size limitations?
What dia coil to be used and the number of turns required. Can any body help me?

#### SgtWookie

Joined Jul 17, 2007
22,210
Here are some numbers for you...
If you took a 3/16" O.D. tube form 3/4" long, and wound on 2,700 turns of #36 wire (about 129 turns/layer, 20 layers) and it will take about 220 feet of wire.

The resulting coil will measure about 90.5 Ohms, drawing about 265mA @ 24V, and 133mA @ 12V, and have about 19.5mH inductance prior to adding the solenoid rod.

Or, you could use about 4000 turns of #38 wire on the same form, about 25 layers, 156 turns/layer, 325 feet of wire. That would measure around 214 Ohms, drawing 112mA@24V, 56mA@12V - and would run quite a bit cooler. This 2nd coil would have 43mH inductance prior to adding the solenoid rod.