Flexdrive V5 resistor question

So I used to think my soldering skills were at least decent if not better then average.

Let's just say my first experience with soldering anything as tiny as a flex was a humbling experience. I had both battery leads soldered on when I noticed that I didn't get the positive lead cleanly though the hole. Rather then leaving wire stands to short something out on the board, I opted to heat the wire back up and pull it out to try again.

Of course when I did this solder filled the hole and no matter what I did I couldn't get it cleaned up enough to get the wire back though. My normal de-soldering braid was just too dang large to do any good, even when trying to trim it smaller.

In my frustration I managed to heat things up a little too much and last resistor fell off (and was quickly lost). I'm going to blame some of this on failing eyesight and shaky hands, but lets face it; I messed up and had no business attempting to solder something so tiny with my tools and skill level.

My question is two parts:
1) Does anyone know what value those resistors are? I'd like to find a replacement. I've had an offer from someone to do the soldering for me, since it's apparent I can't do it.
2) Since I'm only trying to get ~90ma out of this (Default current range), is this resistor even needed?

The documentation says that removing this resistor will lower current slightly when in ranges 2 - 4, but do not state what if anything removing it will do to the default range.

Current Setting:
The Micro FlexDrive has five output current ranges, listed in the diagram below. Each range listed in approximate, there is variation from unit to unit so test the closest range to your desired current and work your way up or down the scale. Removing the end resistor has the effect of decreasing the output current slightly when you are in ranges 2-4. The default 65-100mA range requires no changes. The other ranges require solder jumpers as shown. To adjust and set the diver current, a load is required. A series of 3 or 4 1N4001 diodes and a 1 to 0.2 ohm resistor is recommended for use as a dummy load. Use the Voltage across the dummy load resistor to determine current. Output current is adjusted via the potentiometer trimmer. An insulated screwdriver and a light touch are recommended for adjustment.

Click to expand...

I dont know the value or the type of the resistor but posting a picture of the flexdriver would help a lot !

I know. I can't seem to get a photo with enough detail. My cameras don't have a good macro function.

Here is the image from the manual.

I don't believe removing that resistor has any affect with the range. In fact on the V4 you had to remove it and on the V5's we were removing it for a while with no ill effect until drlava said that it was no longer necessary.:beer:

I am glad I found this thread, I saw it a few months ago & wondered if what happened to jcranmer would ever happen to me. Well last night it did, I accidentally kept my soldering iron on the V5 a fraction of a second too long while dragging a solder blob across the resistors & ended up dragging the last one off. I accidentally removed the same resistor as pictured above & there is no soldering it back on.

jcranmer - what ever came of your issue when this happened to you? Did you still use the flexdrive? What current and output are you getting from it if it did work....? :beer:

You need a tin sucker to do the trick. Hold the solder iron at one side and the sucker on the other side and suck the tin out while it is liquid. Try first at dummy pcb board.

Regarding the solder filling the holes after removing leads, I've never removed wires from a V5 without the holes becoming soldered closed. The fix I've tried several times is easy though.... I've just used a small safety pin (pin has to be thin enough to slide through the V5 lead holes) to press on the solder 'blockage' over the hole & touched the pin with the iron. When the pin heats up the solder softens & the pin pushes through, this has never failed me

The end resistor sliding off hot though on the R side of the flexdrive, that's a new one for me & I'm not sure how the driver will perform without it :thinking:

danefex said:

jcranmer - what ever came of your issue when this happened to you? Did you still use the flexdrive? What current and output are you getting from it if it did work....? :beer:

Click to expand...

Moh offered to take a look at it for me. He was able to get it working. I think all he did was bridge the bottom of the center resistor to the bottom contact point of the missing resistor.

However I still ended up with trouble out of the build and have never went back to check and see if the diode got fried or the driver finally died. It checked out fine with my test load and the diode did work for a short period of time

Keep in mind I was only looking for something around 100ma, so I was on the low range of the driver. I don't know what this resistor may change at the higher levels, but it's worth trying.

I just wouldn't be using it with any exotic diodes just in case.