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Topic: HC-05 activity LED (Read 1 time) previous topic - next topic


Last year I made a silly mistake and bought a couple of HC-05 boards. Reality prevailed and I recently bought a pair of JY-MCU adapter boards. I have soldered the HC-05 modules into place and both are transmitting OK, but I found this out only by good luck as there is nothing from the activity LED on either board. These boards look just the same as the standard store-bought JY-MCU board. 

I soldered six connections
Tx Rx on 1,2
power on 12,13
LED on 24
key on 26

I would expect these to behave in the same way as the original package I have, and it seems too much of a coincidence for both to have dud LEDs yet transmit OK.  So, am I missing something here?


you probably checked this source already, but from your description it seems you are following the schematics for an HC-06 board.
See http://system6.net/download.php?id=1535, compare figs. 5 and 7.

I was thinking of doing the same "silly mistake" of yours, for connecting standalone microcontrollers dedicated to reading and transmitting data from a single sensor. Is it really such a bad choice?


Apr 09, 2013, 05:45 am Last Edit: Apr 09, 2013, 05:47 am by Nick_Pyner Reason: 1
Oh Gawd, I can't believe what I'm reading here. I have that article but I read another which was about the HC-06 only. Yes my module identifies as HC-05 and, since pins 1,2,12,13 are the same, it actually transmits OK.

The module was not a good choice for me, I was just being a cheapskate but, if you know what you are doing and see the problems in advance, it is probably OK.

I even bought a Mega proto board specifically for the job, and got that wrong too. The HC-05 has a pin spacing of 1.5mm. the proto is 0.5", as is also another that I use.  I have never seen a board with 1.5mm pin spacing. If you make your own PCB, no problem.

Also note particularly, that soldering was the least of my problems. I filed the tip of the iron to a sharp point but this might not be necessary.  I still wouldn't be into using flying leads.


connecting standalone microcontrollers dedicated to reading and transmitting data from a single sensor.

I am not quite sure of your intentions here. I am currently using bluetooth just to read data on a laptop, one-way traffic. I have entertained having a Uno read data and transmit to Mega  which is connected to the internet, but when I asked about it on this forum I was studiously ignored and I concluded it was a non-starter.  I now understand that it is possible but I believe the 2.4GHz NRF24s offer a better solution. The HC-05 is just fine for it's original purpose, and will be retained no matter what else goes on, but the reliable range is limited and varies enormously. Don't expect more than 6m if any walls are involved.


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