 Volt meter using a relay: #85 to fuse panel? |
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| Geezer914 |
 Aug 3 2015, 02:40 PM
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#1
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Geezer914  Group: Members Posts: 1,417 Joined: 18-March 09 From: Salem, NJ Member No.: 10,179 Region Association: North East States 
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I am installing a volt meter using a relay. I am running a dedicated wire from the battery to the volt meter. The relay gets wired as follows:
30 Battery in 87 To volt meter 86 To ground 85 To fuse panel Which fuse number on the fuse panel should I connect to 85 on the relay (IMG:style_emoticons/default/confused24.gif) |
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| zambezi |
Aug 3 2015, 02:51 PM
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#2
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Senior Member Group: Members Posts: 711 Joined: 14-April 08 From: Lafayette, LA Member No.: 8,920 Region Association: South East States |
anyone that has key on power. I assume you are wanting to monitor direct battery voltage while running. Most volt gauges don't use a relay though.
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| Geezer914 |
Aug 3 2015, 05:54 PM
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#3
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Geezer914 Group: Members Posts: 1,417 Joined: 18-March 09 From: Salem, NJ Member No.: 10,179 Region Association: North East States
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So which ones have key power from the ignition switch?
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| Steve_R |
Aug 3 2015, 06:02 PM
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#4
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Member Group: Members Posts: 68 Joined: 8-August 12 From: San Diego, CA Member No.: 14,777 Region Association: None |
Why do you wand to use a relay to power the volt meter?
Relays are used to switch high current circuits. A volt meter drawn very little current. You could wire it straight into the switched power. |
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| Spoke |
Aug 3 2015, 06:43 PM
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#5
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Jerry Group: Members Posts: 6,978 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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QUOTE(Steve_R @ Aug 3 2015, 08:02 PM)  Why do you wand to use a relay to power the volt meter? Relays are used to switch high current circuits. A volt meter drawn very little current. You could wire it straight into the switched power. He wants to monitor the battery voltage directly at the battery. This will give the most accurate voltage reading. You should put an inline fuse near the battery for the wire to the voltmeter. This way if you accidentally short the wire at the voltmeter, the wire won't act as the fuse and melt. |
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| Dave_Darling |
Aug 3 2015, 09:10 PM
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#6
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914 Idiot Group: Members Posts: 14,986 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California
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You could use a voltmeter to find out which fuse to plug your relay into. If it has +12V with the key on, and none with the key off, that's the one.
I believe that #8 and #9, among others, qualify. --DD |
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| Geezer914 |
Aug 4 2015, 03:11 AM
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#7
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Geezer914 Group: Members Posts: 1,417 Joined: 18-March 09 From: Salem, NJ Member No.: 10,179 Region Association: North East States
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Thanks Dave, for the reply. (IMG:style_emoticons/default/piratenanner.gif)
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| porschetub |
Aug 4 2015, 04:06 AM
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#8
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Advanced Member Group: Members Posts: 4,699 Joined: 25-July 15 From: New Zealand Member No.: 18,995 Region Association: None |
QUOTE(Spoke @ Aug 4 2015, 12:43 PM) QUOTE(Steve_R @ Aug 3 2015, 08:02 PM) Why do you wand to use a relay to power the volt meter? Relays are used to switch high current circuits. A volt meter drawn very little current. You could wire it straight into the switched power. He wants to monitor the battery voltage directly at the battery. This will give the most accurate voltage reading. You should put an inline fuse near the battery for the wire to the voltmeter. This way if you accidentally short the wire at the voltmeter, the wire won't act as the fuse and melt. could you not just use a Hella fused relay in that case... |
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| Spoke |
Aug 4 2015, 05:40 AM
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#9
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Jerry Group: Members Posts: 6,978 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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QUOTE(porschetub @ Aug 4 2015, 06:06 AM) QUOTE(Spoke @ Aug 4 2015, 12:43 PM) QUOTE(Steve_R @ Aug 3 2015, 08:02 PM) Why do you wand to use a relay to power the volt meter? Relays are used to switch high current circuits. A volt meter drawn very little current. You could wire it straight into the switched power. He wants to monitor the battery voltage directly at the battery. This will give the most accurate voltage reading. You should put an inline fuse near the battery for the wire to the voltmeter. This way if you accidentally short the wire at the voltmeter, the wire won't act as the fuse and melt. could you not just use a Hella fused relay in that case... Yeah, that will give some protection. The fuse should be as close to the battery as possible. Unfused wires become the fuses themselves so the closer the fuse is to the battery the better. |
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