Originally Posted by bigbobed

ppm to base through 4.7k. Base to ground through 22k.

Yes, and since emitter is tied to ground too, then ppm to emitter through both resisters.

Well, I'm outta gas. Sorry I couldn't be more help. See posts 221 & 222.

Thanks for your help. I'm uploading a few pics to see if someone sees something I don't.

For reference, I used the 4.7K, 22K resisters and the MPS2222A NPN
PPM/P modulation selected.
Problem is I seem to have power but when I hold the bind button in during powering on it doesn't ever flash (and I didn't get it to bind to a receiver.)

I had extra resistors and bought an extra NPN so I expanded them out and soldered them on a pcb. Same result as before so I don't think I had a bad transistor the first time.

I'm sorry, but I got to ask this question.

Are you telling the A9 to transmit?

Yep.
Set up model, restart, ready to transmit-? (Hold down bind button) hit YES
Light comes on but doesn't blink.

Testing around more I seem to have fried something.
No more power output. I think I may have momentarily shorted power to ground with my volt meter probe or something. Looks like I have to repair the A9 before I can work more on the dm8 module. Still can't see why it hasn't worked though.

So with the A9 powering the module, the light comes on solid? At that point when you push the bind button, the light/LED should go out, (low power/range test mode). Can't say what this scenario will prove, but would verify the button/switch is functioning.
Got a friend with a Futaba or appropriate Hitec that the module will plug directly into?
Things are pointing to a defective module I think.

Sorry to hear about possible A9 damage.
As BigBobed mentioned, I also have done a few of these without a problem.
Sometime *^#@* happens.

Actually, the light didn't go out when I pushed the button after the module was powered. It does seem to denote that the module isn't working right. Maybe just the button on the module isn't working. Have to wait until I get the Tx fixed I think now. This is becoming an expensive module!

Originally Posted by LowWatts

So with the A9 powering the module, the light comes on solid? At that point when you push the bind button, the light/LED should go out, (low power/range test mode). Can't say what this scenario will prove, but would verify the button/switch is functioning.
Got a friend with a Futaba or appropriate Hitec that the module will plug directly into?
Things are pointing to a defective module I think.

Sorry to hear about possible A9 damage.
As BigBobed mentioned, I also have done a few of these without a problem.
Sometime *^#@* happens.

Originally Posted by mulicheng

Thanks for your help. I'm uploading a few pics to see if someone sees something I don't.

For reference, I used the 4.7K, 22K resisters and the MPS2222A NPN
PPM/P modulation selected.
Problem is I seem to have power but when I hold the bind button in during powering on it doesn't ever flash (and I didn't get it to bind to a receiver.)

I had extra resistors and bought an extra NPN so I expanded them out and soldered them on a pcb. Same result as before so I don't think I had a bad transistor the first time.

Did you buy the transistors from radio shack? According to the pinout i found on the web (http://images2.powerreviews.com/medi...167818_raw.jpg) you have the collector and emitter reversed.
why dont you disconnect the module, and replace the a9 ppm input with a 3.3v voltage to test the output at the collector first? you will need to pull up the collector with a 1k resistor for example. the voltage you see on the collector will be the reverse of the voltage you apply on the a9 side of the circuit.

your resistors are outside the range originally specified too. the voltage applied at the base is going to be different than as designed. i'm too lazy to figure if this will affect the circuit negatively or not
i can be sure having the C-E connections reversed will :-)

Here is what I have.

Yeah I have the same packaging as LowWatts.

The way I understand that picture when they say bottom view they mean if you look at it with the pins pointing toward you. I'm pretty sure I wired it correctly. You can see the flat side of the NPN in the pic I uploaded. Is the pin I wired to ground not pin 1, or the emitter?

I started to test the voltage external to the A9 to make sure the NPN was working right. (That was those two extra wires in my picture that I said to ignore). I'm out of resisters though. I could wire a few of the 4.7k resisters together to make a ~1k resister I guess. Otherwise I'll just pick up some more resisters at Radio Shack.

Originally Posted by juice555

your resistors are outside the range originally specified too. the voltage applied at the base is going to be different than as designed. i'm too lazy to figure if this will affect the circuit negatively or not
i can be sure having the C-E connections reversed will :-)

There were a few references to using the 4.7k and 22k resisters in this thread. Radioshack doesn't have 6k and 13k resisters. Or at least not in stock at most of the stores.

Here is the document I found earlier that helped me determine the collector was where I put it too:

http://tinyurl.com/d8e7wft

OK, curiosity got the better of me. I wired my 3 extra 4.7k resisters in parallel to get ~1.5k resister for a pull-up on the collector. Tested with an external 6V battery pack that has tap for 3V. When I apply 0V to base, Voltage on collector is 6V. When I apply +3V to base, V goes down to approx 33mV. I believe that is the correct operation and that I indeed wired the circuit correctly. Which further supports the theory that my dm8 module just has an issue. I'll see if I can find someone who can test the dm8 in a futaba Tx.

yes, operation sounds good to me. thats how my circuit behaved before I connected to module.
thats too bad. sounds like you are doing everything correctly.
i would do the same thing as you suggested and try on a futuba to eliminate the possiblity of the module being at fault.
hopefully the module wasnt damaged in your tests.
good luck