Resister Install without a board

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Ramdude
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Resister Install without a board

Post by Ramdude »

I would like to install 2 ceramic type resisters in-line on a wire.
Is there some sort of holder for this or do I just solder them in and fix up some sort of support and insulation for it.<p>It's for an automotive application and I don't want bare resisters hanging under the dash.
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dacflyer
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Re: Resister Install without a board

Post by dacflyer »

what size resistors are they?
1/4 watt - 1/2 watt ???
if they don't get hot,,,you probably can solider on the leads then heat shrink them,,,<p>theres a thought :D
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jwax
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Re: Resister Install without a board

Post by jwax »

Ceramic resistors are usually used where some power must dissipate, meaning open to the air or attached to a heat sink. Depending on their size, best to metal clip or strap them to a metal wall, away from heat-sensitive material. Allow airflow, and shrink wrap the wires and joints. ;)
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paulrevelcet
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Re: Resister Install without a board

Post by paulrevelcet »

What will said wire be running from and to?
Ramdude
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Re: Resister Install without a board

Post by Ramdude »

They are 1/2W carbon film, 330ohm and 68ohm, one each. Will be connected to a relay that switches to ground and the other end connected to a 2.5vdc ckt.<p>Expected "on" times for this ckt are 1-7 minutes, I have tested it to only 3 minutes so far and no burn out. Do you think these 2 resisters will get too hot?<p>Basically I am wanting to reduce v on that ckt but only momentary up to 7 min. max.
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jwax
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Re: Resister Install without a board

Post by jwax »

Ignore my last post, Ramdude- that was for ceramic resistors-high power.
Your resistors ought to be fine in shrink tubing.
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Ramdude
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Re: Resister Install without a board

Post by Ramdude »

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by jwax:
Ignore my last post, Ramdude- that was for ceramic resistors-high power.
Your resistors ought to be fine in shrink tubing.
<hr></blockquote>Do you mean completely covered or shrink just on the ends where the connection is made?
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jwax
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Re: Resister Install without a board

Post by jwax »

Not sure of your wiring, but even if you put the two resistors in series, across the 12 volts, you'd still be OK having them fully shrink wrapped. That's resistors and joints.
Try it and see!
;)
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jollyrgr
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Re: Resister Install without a board

Post by jollyrgr »

If you are using 1/2 watt resistor (regardless of its makeup) it should NEVER get hot. If it does, you are over stressing it. <p>You mentioned that the circuit was a 2.5V supply. Let's do the math. If the worse case were to happen and the full 2.5V appeared across the 68 Ohm resistor, you would get the following:<p>E = I*R
and
P = I*E<p>We have two knowns right off the bat; E (voltage) and resistance (68 Ohms). Solving the first eq for I gives:<p>I = E/R<p>Sub this new Eq into the I parameter of the second Eq gives:<p>P = (E^2)/R<p>P = (2.5*2.5)/68<p>P = 0.1 watts. Thus the 1/2 or 0.5 watt resistor should work fine.<p>Just what are you trying to do? <p>As to your questions, you could heat shring the entire resistor or just the wire connections. It it is not critical for just a couple resistors and a relay. Are you sure that you mean 2.5 volts and not something like 12.5 volts?
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Ramdude
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Re: Resister Install without a board

Post by Ramdude »

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Jolly Roger:
Just what are you trying to do?
Are you sure that you mean 2.5 volts and not something like 12.5 volts?
<hr></blockquote><p>I have a 5v reference ckt that has a sensor on the other end that pulls the v down to 2.5v average during engine operation, this is the factory ckt.<p>Tapping into that ckt and pulling it to ground through 398 ohms using a switch and relay gives me the desired result on that 5v reference ckt.<p>I could use just a switch but I wanted a lighted switch so that meant using a relay cuz any DPST illuminated sw would be a rectangle rocker that I didn't care for, I wanted a toggle.<p>The sw illumination is 12v supplied and commands the relay but the relays output to the ckt I want to control is ground so the 12v is isolated from the control ckt.<p>So my original question was how best to install 2 resisters in the wire rather than on a typical board.<p>Should I set them side by side or in-line like one after the other?
Heat wise- can I heat shrink over the top of the ceramic portion?
Is there some sort of holder available for an install like this such as an in-line fuse holder but for a resister?<p>I'm proly making it harder than it is and just need to cut the wire, solder in the resisters and heat shrink over it all to protect.
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Dave Dixon
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Re: Resister Install without a board

Post by Dave Dixon »

Ramdude,
What "ceramic portion"?????
I thought these were carbon film resistors.
Dave
Ramdude
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Re: Resister Install without a board

Post by Ramdude »

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Dave Dixon:
Ramdude,
What "ceramic portion"?????
I thought these were carbon film resistors.
Dave
<hr></blockquote>Well maybe a poor choice of words as I always knew resisters that looked like this as ceramic:<p>
Image<p>The two resisters I will be using are listed as carbon film- this one and this one.<p>I learned that wiring them side by side won't work and they need to be in-line- one after the other to obtain my end result.
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Dave Dixon
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Re: Resister Install without a board

Post by Dave Dixon »

Hey - me again,
I've got a .jpg to send you. If you
send me your email to me at [email protected]
I'll send it your way.
Dave
I tried to attach it, but I couldn't figure
out how, as it's not posted on the WWW.
Ramdude
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Re: Resister Install without a board

Post by Ramdude »

<blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr>Originally posted by Jolly Roger:
[QB]P = 0.1 watts. Thus the 1/2 or 0.5 watt resistor should work fine.[QB]<hr></blockquote><p>Would that mean a 1/8 or 1/4 watt would do also?<p>I did locate a single 1/4w 390 ohm that could also work and a 3w 390 ohm. Using a single resister would simplify the install.<p>If I change to a different power rating will that change the v drop on the ckt?
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