Current setting

[The_Muffin_Man]

hey guys,

So heres the deal.  I got a v4 flexdrive today and tried setting the current with the test load i also made today.  I had a test load before (a rkcstr one) but it died in an unfortunate accident.  (dont ask  ;D :-[).  So my test load has 6 1N4001 dioes and a 1 ohm resistor.  I have it all hooked up to my driver and my DMM is set to V (it goes to mV when i hook the driver up) but the least amount of current that i can get is 165mA which is way too much for a phr diode (for it to last a long time)


Can anyone shed any light on this?

Thanks

Here are some pics(sorry they are so big :-[):

 

[The_Muffin_Man]

heres another of the DMM:

 

[daguin]

This is the reading he's getting with the flexdrive in the "stock" configuration.  It should be reading between 65mA-100mA.

I'm missing something here.  What are we doing wrong?  What am I missing?

Peace,
dave

 

[The_Muffin_Man]

Thankyou for resizing those dave

Yes this is in the stock setting. The green wire on the test load goes to the - output and the red goes to the positive output. I am putting the positive DMM probe on the right side of the resistor and the negative on the left.

If anyone wants a certain picture of something i am happy to take it

Thankyou

 

[The_Muffin_Man]

I just thought of something. If the resistor wasnt a 1 ohm one it could be messing up the reading (boosting it up).

Does anyone know of an equation to "fix" the reading if it is a different resistor. I also have a 10 ohm resistor if anyone knows the equation to "fix" the reading for that.

 

[lasersbee]

I just thought of something.  If the resistor wasnt a 1 ohm one it could be messing up the reading (boosting it up).  

Does anyone know of an equation to "fix" the reading if it is a different resistor.  I also have a 10 ohm resistor if anyone knows the equation to "fix" the reading for that.  

Your first picture shows your 1 Ohm resistor's colors.....

Is the first band color (on the right in your photo) Red or Brown... :-? :-?


Jerry

 

[The_Muffin_Man]

[quote author=The_Muffin_Man link=1236656598/0#4 date=1236725156]I just thought of something.  If the resistor wasnt a 1 ohm one it could be messing up the reading (boosting it up).  

Does anyone know of an equation to "fix" the reading if it is a different resistor.  I also have a 10 ohm resistor if anyone knows the equation to "fix" the reading for that.  

Your first picture shows your 1 Ohm resistor's colors.....

Is the first band color (on the right in your photo) Red or Brown... :-? :-?


Jerry[/quote]

Im pretty sure its red

 

[lasersbee]

Well... if it's Red then you have a 2 Ohm resistor and
your reading should be multiplied by 0.5.... (169.4 / 2 = 84.7mV=87.4mA)...

If a 1 Ohm resistor gives you (1mV=1mA)...
then a 2 Ohm resistor gives you (1mV=.5mA)

Jerry

 

[The_Muffin_Man]

Well... if it's Red then you have a 2 Ohm resistor and
your reading should be multiplied by 0.5.... (169.4 / 2 = 84.7mV=87.4mA)...

If a 1 Ohm resistor gives you (1mV=1mA)...
then a 2 Ohm resistor gives you (1mV=.5mA)

Jerry

Ill try that out. Its for a blu-ray though

 

[lasersbee]

[quote author=lasersbee link=1236656598/0#7 date=1236732514]Well... if it's Red then you have a 2 Ohm resistor and
your reading should be multiplied by 0.5.... (169.4 / 2 = 84.7mV=87.4mA)...

If a 1 Ohm resistor gives you (1mV=1mA)...
then a 2 Ohm resistor gives you (1mV=.5mA)

Jerry

Ill try that out.  Its for a blu-ray though  [/quote]

It doesn't matter what it is for.... If you use that 2 Ohm resistor the formula
is (2mV=1mA)... reading on your meter..

Jerry

 

[billg519]

On my screen, that band looks orange, for a 3[ch937] resistor ... (You'd need to multiply by 0.333)
Measure it with your DMM set to ohms and you'll know for sure what to do.

 

[The_Muffin_Man]

what do i measure on my DMM? the resistance across the resistor? So should i desolder the resistor and test it?

 

[The_Muffin_Man]

i de soldered my resistor and measured the resistance across it and it read 2.9-3 So i am assuming it is a 3 ohm resistor. So all i do is multiply by .333?

Thanks

 

[lasersbee]

i de soldered my resistor and measured the resistance across it and it read 2.9-3 So i am assuming it is a 3 ohm resistor.  So all i do is multiply by .333?

Thanks

If it is a 3 Ohm resistor.. the color band will be Orange not Red...
If it is a 3 Ohm resistor... then yes.. you multiply your reading by .333 to get
the current through your circuit in mA...

Jerry

 

[The_Muffin_Man]

Sounds good. One last question. I was adjusting the pot and the current jumped from 101 to 320. (this is after i changed the range to 100-312). so that is about 107mV which is 107mA. Correct?

Thanks