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Author Topic: Switched power for mobile in Chevy S10  (Read 6252 times)
KK4LGR
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Posts: 53




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« on: December 26, 2013, 03:52:28 PM »

Howdy crowd,

I just carried my new FT-1900 out to my truck and discovered that it would fit perfectly where the ash tray goes.  Any late-model S10 owners should know what I'm talking about.

There's a little light bulb inside the ash tray that's always on when the key is on.  Now I'm going to run the power straight from the battery as per Yaesu and Chevrolets instructions, but could I put a relay in the power lines powered by that light circuit so that the radio shuts off with the ignition key?  Would having a relay in the cab that close to the rig be problematic due to EMF?

Thanks,
Adam
KK4LGR
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"Well I'm sure glad we've got these ham radios to talk on."
--Unidentified station heard on 2 meters
G8YMW
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Posts: 256




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« Reply #1 on: December 26, 2013, 04:22:31 PM »

Just had a root about on Alan Applegate's site (K0BG.com) under "Wiring and grounding"

Here's a copy/paste from there

Using ignition-controlled relays to switch power off and on to amateur radio equipment is a common, but ill-advised, practice. Advocates believe that doing so will protect the equipment in question from starting motor transients. That is no doubt true, but how about the transients when the relays are energized? The truth is, they're a waste of time, and just one more failure point. The argument that they protect the owner's memory when they fail to remember to turn off their transceivers, is just as lame. Fact is, all but a couple of modern transceivers (no matter their frequency coverage) have built in timers which automatically shut off the transceiver after some preset time delay. If you just have to be warm and fuzzy about transients, then place a large, properly-fused, Farad-sized super capacitor close to the transceiver side of the power cable.

If you just gotta have remote relay control, Perfect Switch® is the answer (also see Power Protectors below). They employ FET technology, so there are no contacts which could fuse together in a dead-short scenario. Fact is, drawing current over their rating will cause them to disconnect, and require a reset. This is about as fail-safe as you can get. Proper fusing is still required, however.
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73 de Tony
Sent by WW2 Royal Navy signal lamp
KK4LGR
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Posts: 53




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« Reply #2 on: December 26, 2013, 05:23:23 PM »

Yeah that pretty much answered my question.  My main concern was leaving the power on and draining the battery, and I had handy (and soon to be redundant) wiring.  I'm sure as heck not gonna power the rig from the adjacent cigarette lighter plug! Wink

Thanks and 73
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AA4PB
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Posts: 12985




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« Reply #3 on: December 26, 2013, 05:26:49 PM »

Sure you can place a relay in line and power it from the light. You probably want to make sure that the light is on the ACC line (comes on if the key is placed in the ACC position). Using the ACC line will ensure that 1) power is removed before engaging the starter and restored after the starter is disengaged. The starter is the biggest source of spikes. The ACC line will also enable you to power the radio without having the engine running or the ignition on. There should be no RFI issues with the relay being close to the radio. Just be sure that the relay contacts are plenty large to handle the peak radio transmit current draw.

I do not agree that there is any danger to using the relay. We did it for years in commercial radio business. In addition, some modern radios leave output transistors and other devices connected to the power line even when the radio is switched off. A component failure could drain your battery if you don't have a relay installed. The other advantage to the relay is that if you take the keys out of the ignition when you leave then you are guaranteed that the radio is off.

By the way, opening and closing the series relay contacts is not going to generate any spikes. Its no different that turning on/off your AC power supply in the shack.
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M6GOM
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« Reply #4 on: December 27, 2013, 03:26:59 AM »

Just had a root about on Alan Applegate's site (K0BG.com) under "Wiring and grounding"

Here's a copy/paste from there

Using ignition-controlled relays to switch power off and on to amateur radio equipment is a common, but ill-advised, practice.

Rubbish. Alan and I disagree quite strongly on several aspects of his website when it comes to powering radios. I speak from a strong automotive and electronics engineering background. I'm not quite sure what his qualifications in this respect are but anyone who claims a 5W HT with no faults can draw so much current from a 12V AUX socket that it sets the car alight needs to have their advice treated with a large pinch of salt.

Please don't give any further advice on powering mobile installations.

Yours sincerely, a former vehicle mechanic and automotive electrician currently half way through a BEng (Hons) Electronics Engineering degree....

To the OP. What you are wanting to do will work just fine but make sure you have the correct rating of relay, I'd go for 20A just to make sure.

One word of advice though is before deciding to install there make sure there's plenty of ventilation. I don't know that dashboard but in many where the ashtray goes it is a solid recess rather than a hole in the facia so you would get a massive heat build up.
« Last Edit: December 27, 2013, 03:30:22 AM by M6GOM » Logged
K7RBW
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Posts: 398




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« Reply #5 on: December 27, 2013, 08:26:55 AM »

In my car, I just use the Automatic Power Off feature of the radio. Less hassle than a relay and the radio doesn't draw that much current on receive/idle so leaving it on for an extra 30-60 minutes (or for however long you want to configure it) isn't going to hurt the battery.

Check p.63 of the FT-1900 manual: http://www.yaesu.com/downloadFile.cfm?FileID=7879&FileCatID=150&FileName=FT%2D1900R%5FOM%5FEH023N111.pdf&FileContentType=application%2Fpdf
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KK4LGR
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Posts: 53




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« Reply #6 on: December 31, 2013, 05:10:08 PM »

@M6GOM,

I could probably get away with it, but I think I'm just going to use the time-out timer on the radio, at least at first.  Wiring in a relay isn't that hard.  I'm pretty sure that light is on the ACC switch, but I'll have to check.  Another idea I have is to wire in a slide switch to shut that bulb off when the ash tray is closed, because I don't need to light the inside of my dashboard *rolls eyes*

The ash tray on the late model S10s hinges down from below the dash board, so it would hang just below the dash board with a little bit of trim on either side.  The FT-1900's heat sink is on the bottom of the radio, and it would be free and clear with nearly a foot of clearance from the floor.  There's a big, solid plate of metal just inside the recess, so I'm more and more considering hanging the radio from a suction cup mount if I can find one strong enough (or I'll get a mobile rig with a remote display head and put it there).  That kind of mount would hang the rig at least an inch or two below the dash.

I'll post a picture or ten of the cab in question, show you what I mean.  It's basically the only place I can think of where a radio wouldn't be in the way.
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"Well I'm sure glad we've got these ham radios to talk on."
--Unidentified station heard on 2 meters
VO1GXG
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Posts: 60




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« Reply #7 on: February 16, 2014, 07:18:40 PM »

In the commercial two way radio world Motorola would supply a 12v switch leg and a 12v primary leg to go straight to the battery. Newer radios just had straight through primary, the majority of two way radio shops i have seen and worked for would use a " Fuse tap " to tap off or replace a switched power source from the vehicles fuse box. This is how i have done my own VHF radios in my Jeep.  perfectly fine for 10 amp draw at 50 watts.  20-30 amp draw for HF? thats where my relays with a switched tap from the fuse box comes in.  Chances are the wiring harness for the bulb is probably smaller then 18awg so you should not wire the radio directly to that but it does make a great switch leg for a 20-30 amp relay!
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K5LXP
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« Reply #8 on: February 17, 2014, 07:15:37 AM »

I too disagree with K0BG on this one.  While indeed radios should tolerate load dumps, starting transients and off-on-off-on power cycling during starting, I choose not to put them through it.  

I use a simple RC time delay circuit dead-bugged to an ice cube relay to power the radio in the car.  It's about a 10 second delay to turn on which is more than plenty of time for the engine to turn over and the alternator to stabilize.  If nothing else, it saves wear and tear on the radios' power switch.

You can also buy modules that sense voltage and turn the radio on and off without having a separate input for switched ignition and provide for a settable turn off delay.  November 2012 QST had an article for building your own. 

LGR, you may want to be sure the ash tray light isn't on the dimmer circuit.  You would have to use a different switched ignition circuit in that event.  

I used the ash/drink tray in my Marquis for a radio and since it was dimmable, I relocated the ash tray light to the front of the tray to serve as a soft illumination for the front of the radio.



Mark K5LXP
Albuquerque, NM


« Last Edit: February 17, 2014, 07:28:02 AM by K5LXP » Logged
N6AJR
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Posts: 9921




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« Reply #9 on: February 17, 2014, 01:24:54 PM »

I use a device called a constant duty solenoid.  it operates just like a Ford starter relay, but is made to stay on for long periods, we used them to control the red lights on our emergency equipment.  you can get them from an automotive store for 10 to 30 bucks depending on load capacity, ( I like 150 amps constant /300 surge) and they mount anywhere and you just need a switch and some thin wire ( I used speaker wire) to run the 12 v control line.
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K1CJS
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Posts: 6055




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« Reply #10 on: February 18, 2014, 05:44:07 AM »

...I used the ash/drink tray in my Marquis for a radio and since it was dimmable, I relocated the ash tray light to the front of the tray to serve as a soft illumination for the front of the radio....

Nice neat and compact setup, Mark.  I had considered something similar for my Grand Marquis, but wanted to keep the cup holder!  Yep, the cup holder was more important.   Grin 

I ended up building a rig stand that would fit between my 45/55 front seat that was angled toward the driver side.  It held a 2 mtr rig and a small scanner--and fit closely to the pulled out ash/drink tray.  73!
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W7HBP
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Posts: 166




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« Reply #11 on: February 23, 2014, 11:12:52 AM »

Howdy crowd,

I just carried my new FT-1900 out to my truck and discovered that it would fit perfectly where the ash tray goes.  Any late-model S10 owners should know what I'm talking about.

There's a little light bulb inside the ash tray that's always on when the key is on.  Now I'm going to run the power straight from the battery as per Yaesu and Chevrolets instructions, but could I put a relay in the power lines powered by that light circuit so that the radio shuts off with the ignition key?  Would having a relay in the cab that close to the rig be problematic due to EMF?

Thanks,
Adam
KK4LGR

That is exactly how I wire all my rigs. Power right to the battery, switched relay to shut it off when I exit. A Bosch type 30 amp automotive relay works great, terminal #30 to battery, 86 to ground, 85 to your light bulb and 87 to the radio power.
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