Constant Current Dummy Load Kits

[J4e8a16n]

I have the bg version.

Do I read ok when I see that the 5678 pins should be joined in the b version (right side of the sheet)?

JP

[Rerouter]

i had connected mine up according to the A diagrams diagram, (common ground) if your clever there is a way to fold the resistors against the back of the meter so that it doesnt add more than 5mm on the back of the meter using through-hole parts,

[J4e8a16n]

Hi,

Yes I was thinking to put the resistors under the pcb.

[J4e8a16n]

there is the A version (9V), and the B Version (5V) but there is also the BG varient that is the b version thats comapatible with a common ground, make sure you have the right one, else you need an isolated supply to the meter,

I have the CX101BG 5V common ground

So if I read you right I can use the wiring diagram on the left side of the shema I posted?

[Rerouter]

yes......

[HardBoot]

Constant current loads confuse me, why, how often do you have a situation where you really need to test that? Not too often.
Generally you just want a variable resistor, electronically controlled it could also be a CC load.

[mariush]

I'd like to give this circuit a try.

Problem is i usually order from Farnell batches of components so I'd rather not waste money on Mouser or RS-Online shipping... but Farnell don't have this MTP3055 in Europe.

Could any of you more knowledgeable please tell me if this IRFIZ34NFBF is compatible :  http://ro.farnell.com/international-rectifier/irfiz34npbf/mosfet-n-55v-19a-to-220fp/dp/8649111

 MOSFET, N, 55V, 19A, TO-220FP
Transistor Polarity: N Channel
Continuous Drain Current Id: 19A
Drain Source Voltage Vds: 55V
On Resistance Rds(on): 40mohm
Rds(on) Test Voltage Vgs: 10V
Threshold Voltage Vgs Typ: 20V
Power Dissipation Pd: 31W

The MTP3055 is listed as

    N CHANNEL MOSFET, 60V, 12A, TO-220
    Transistor Polarity: N Channel
    Continuous Drain Current Id: 12A
    Drain Source Voltage Vds: 60V
    On Resistance Rds(on): 180mohm
    Rds(on) Test Voltage Vgs: 15V
    Threshold Voltage Vgs Typ: 15V


It's the closest in specs I could find that's also available in EU stock. 

Other than this I'm thinking of using 2-3 x 10ohm 7w resistors instead of those 10 1/4w resistors - I'm going to order a few of those for another project and Farnell sells only in packs of 5 so I'm going to have these handy. Would this be an issue?

Oh one more question: What happens if I'd power the op amp with 3.3v or 3.6v?  Thinking of using a LDO with such fixed voltage so that i could power the board from 4.5-5.5v (3xAA or usb port) - the mcp6004 datasheet says it will work at such low voltage.  I'm guessing the load this board could generate would be much lower, probably have to tweak the resistor values. I'm not sure if  the fet would be affected in a way.

Yes, sorry about these probably very simple questions,  I should probably watch dave's video and see the explanations in the video and the blog page. 

[J4e8a16n]

Oh, jeez. I'll have to look back through my notes.

Here is some result for the MCP 6004

pin 3             pin 1                          pin 10                   pin 8
.020V             .56V                           .18V                    2.165V
.11                 .66V                           .22V                    2.33V
1.0                 1.08V                         .33V                    2.36V

Does the chip is OK? Do you have approximatively the same readings?

JP

[J4e8a16n]

I recreate the circuit on a breadboard with a brand new MCP6004 , here are the result:
pin 3             pin 1                          pin 10                   pin 8

.266                .266                         .110                       1.966
1                    1                               .412                       2.414

Does the chip is OK? Do you have approximately the same readings?

I guess that the first opamp (pins 123) is there only to stabilise the input voltage on pin 10: is that it?

Thanks for your attention.
JP