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I've built a reg from parts from work and its not working properly!


I've got it putting out 7v, but only 1.2 amps. How much amperage does the gauge need? I know my gauge works, but not with this current setup?
 

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Monkey with a Football
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The regulators are one amp regulators so it has to be less than that.
I would recommend the fixed 3 terminal, 1 amp TO-220 regulators (7807) over the variable regulators because they are simpler, can't get out of adjustment and won't drift over wide ambient temperature ranges.
 

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Thanks! I just needed to get that info so I can look for parts at work! I work at a place building aircraft electronics so we have a huge inventory of components available. I just need to search the database and find if we have anything that can meet my needs!
 

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Monkey with a Football
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Get your buyers to sample you some industrial temp 7807's. It's a common part but the voltage is not one that gets stocked a lot.

The whole 7800 series is a common with different prefixes as in LM-7807. This will vary per manufacturer.

Don't confuse them with the 7900 series which is the same thing in a negative voltage.

As I stated earlier, I'm not a fan of the more available LM-317-T series or any other adjustable regulator in a hostile environment.
 

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I'm dumb! I started another topic thinking I'd not posted about it!! DUMB ME!

Anyhow...


I've built a reg from parts from work and its not working properly!


I've got it putting out 7v, but only 1.2 amps. How much amperage does the gauge need? I know my gauge works, but not with this current setup?
 

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Monkey with a Football
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smocksam wrote:
I'm dumb! I started another topic thinking I'd not posted about it!! DUMB ME!

Anyhow...


I've built a reg from parts from work and its not working properly!


I've got it putting out 7v, but only 1.2 amps. How much amperage does the gauge need? I know my gauge works, but not with this current setup?
I guess your gauges probably pull no more than 1/2 amp. The reason I say this is that the original reg was 1 amp with a crappy heat sink and it ran fairly hot.

My experience would be that I would guess that it was drawing between 400 and 800 milliamps to heat like that with that regulator with that heat sink mass.
 

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Hrm.... I wonder what I've got going wrong then.

I've got 7v and 1.2 amps, but my gauges weren't moving??? I'll have to play with it some more tomorrow and see what I can see.
 

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I got to thinking about it and before I started messing with my gauges, I'd just hooked an alkaline 9v battery to the gauge and it moved it. So this reg I've built should be more than ample.

I'm wondering if my darned gauge or sending unit failed when the last reg did? I'll have to pull out the meter tomorrow and start checking. I'd hope it was the gauge and not the sending unit, that thing looks like a bear to replace!
 

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smocksam wrote:
I got to thinking about it and before I started messing with my gauges, I'd just hooked an alkaline 9v battery to the gauge and it moved it. So this reg I've built should be more than ample.

I'm wondering if my darned gauge or sending unit failed when the last reg did? I'll have to pull out the meter tomorrow and start checking. I'd hope it was the gauge and not the sending unit, that thing looks like a bear to replace!
It's easy to see that you have 7v.

How do you know you have 1.2 amps?

Are you measuring current while in circuit? If you are and you see 1.2 amps, are you also seeing 7v under load at the same time?

Does the 9v batt still move the guages?
 

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Actually the sending unit is very simple to replace. Hardest part is pulling the seat.

Sounds to me like you need to start chasing wires and such. It is a very simple system and if you work on Avionics then it should be extremely easy to troubleshoot. The sending unit is nothing but a variable resistor that drops the 7 volts "in" to indicate what ever level the fuel is.
 

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I'll have to pull the gauges off to check and see if they still move or if the sending unit isn't working.

It's putting out 1.2 amps while just sitting there. I've not tried to check it under load yet.

As far as the sending unit goes???? Why would I need to pull the seat? That would be for the fuel gauge wouldn't it?
 

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Monkey with a Football
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smocksam wrote:
It's putting out 1.2 amps while just sitting there. I've not tried to check it under load yet.
It's not putting out ANY amps just sitting there. There has to be a complete circuit to make current flow. Current only flows when there is a load on the output of the regulator.

That's why I was asking if you saw 1.2 amps AT 7 Volts when loaded by the guages and on.
 

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That is what I thought we were discussing?? The Fuel gage system is also powered by the 7v Reg. Is that working but not your temp system??
 

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I didn't put it inline with the gauges, I just hooked the output to ground and it was putting out around 1.2 amps. I didn't try to see what it did while hooked to the gauges cause the wife was yelling at me! It's amazing how she thinks her birthday is more important that working on the bike :)
 

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smocksam wrote:
I didn't put it inline with the gauges, I just hooked the output to ground and it was putting out around 1.2 amps. I didn't try to see what it did while hooked to the gauges cause the wife was yelling at me! It's amazing how she thinks her birthday is more important that working on the bike :)
Ok the meter shunt was the load. At that point, if you had a second meter, and you measured the voltage at the same time, you would have seen about 1 volt at the same time.

What do you see for voltage when you put the regulator in circuit in the bike?
 

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I'll have to check and see tomorrow. I did it last night and want to say it was 7v, but I'm not sure.
 

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smocksam wrote:
I'll have to check and see tomorrow. I did it last night and want to say it was 7v, but I'm not sure.
Ok, if it turns out to be 7v break the output voltage line and insert the current meter in series with it and see how much current you are pulling. Also take note of the heating of the heat sink at the regulator.
 
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