 Voltage drop on relay circuit?, 12v down to 10.5v |
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| IronHillRestorations |
 Jul 11 2017, 11:46 AM
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I. I. R. C.  Group: Members Posts: 6,813 Joined: 18-March 03 From: West TN Member No.: 439 Region Association: None 
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I'm making a harness that needs a power circuit switched via relay.
I've got generic Bosch style 5 pin relays, and I'm seeing a voltage drop on the power out side of the relay. It's rare that I make a harness that needs a relay, and in the few that I've done with a relay circuit, this has never been reported as a problem. I'm not an electrical engineer, but I always thought a relay was just an electro-mechanical switch and I should be getting the same voltage on the output. Just to be clear for those who do know more about this than me, none of the wires that I'm using to test this are more than 24" long and none are less than 14 gauge wire. The relay power is for a coil pack, so I'm sure that needs a good 12+ volts. |
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| Bartlett 914 |
Jul 11 2017, 12:27 PM
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Advanced Member Group: Members Posts: 2,218 Joined: 30-August 05 From: South Elgin IL Member No.: 4,707 Region Association: Upper MidWest |
If you can, measure at the relay input and output. There should be zero volts. If measuring from the ground, then both input and output should read the same voltage (12 volts). If there is a difference, then the relay is bad, There should be no drop at the relay contact. It the circuit has a large load, then there can be a voltage drop across the length of the wire. Shorter wires or larger gauge in the answer
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Posts in this topic
Perry Kiehl Voltage drop on relay circuit? Jul 11 2017, 11:46 AM
914Sixer Are all the relays showing the same test? Jul 11 2017, 12:03 PM Perry Kiehl Yes, Mark they do. I currently have only cheap on... Jul 11 2017, 12:14 PM danschy Pretty hard to get a significant voltage drop acro... Jul 11 2017, 12:54 PM jd74914 Do you know the circuit load (current)? How are yo... Jul 11 2017, 12:55 PM Perry Kiehl This is all bench testing. I'm using a batter... Jul 11 2017, 01:36 PM Spoke It is possible that the battery charger is full-wa... Jul 11 2017, 02:16 PM
Dave_Darling
It is possible that the battery charger is full-w... Jul 11 2017, 05:59 PM Spoke What voltage do you measure at the output of the c... Jul 11 2017, 02:19 PM Perry Kiehl I feel sooo stuuupid! It's the battery ch... Jul 11 2017, 08:50 PM 914_teener
I feel sooo stuuupid! It's the battery c... Jul 12 2017, 07:06 PM Spoke It's called "fog in the cockpit". Ha... Jul 11 2017, 08:52 PM Perry Kiehl
It's called "fog in the cockpit". H... Jul 12 2017, 08:31 AM Perry Kiehl The smart guys figured it out right away. Jul 12 2017, 07:44 PM |
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