Search found 1629 matches

by lyndon
Fri Aug 01, 2008 3:26 pm
Forum: Wireless/RF
Topic: how to know my RN-41 works or not
Replies: 11
Views: 2681

This is how my RN41 is configured: All GND pins to ground (I think there are 6 of them) Vdd to 3.3V CTS looped back to RTS (pins 15, 16) LED on pin 21 with 330ohm resistor to Vdd. Tx & RX to a microcontroller. All other pins N/C At power up the LED blinks quickly then slows down after 1 minute when ...
by lyndon
Fri Aug 01, 2008 6:30 am
Forum: Wireless/RF
Topic: how to know my RN-41 works or not
Replies: 11
Views: 2681

Connect an LED to pin 21. It should blink on power up.
by lyndon
Thu Jul 31, 2008 10:24 am
Forum: SparkFun Product Questions
Topic: nimh battery charger
Replies: 5
Views: 1684

The reason you shouldn't charge the cells in parallel is really because then it's harder to tell when the cell is fully charged and you should stop charging it. If you can monitor and control the cells individually there's no reason not to do it. There are two relatively simple solutions: 1) trickle...
by lyndon
Wed Jul 30, 2008 4:52 pm
Forum: SparkFun Product Questions
Topic: very thin mirror glass
Replies: 3
Views: 1349

Anchor Optics sells Edmund surplus at much lower prices. Here are some thin first surface mirrors:
http://www.anchoroptics.com/catalog/product.cfm?id=360
by lyndon
Wed Jul 30, 2008 4:48 pm
Forum: Wireless/RF
Topic: RN-xx external antenna?
Replies: 0
Views: 523

RN-xx external antenna?

Has anyone removed the chip antenna on an RN41 and replaced it with a stub or dipole ant? How did it work? I can't find any reference to this on their site and I'm working on something that will be housed in a metal enclosure so it needs an external antenna. I'm looking at the Sena units with extern...
by lyndon
Thu Jul 24, 2008 10:21 am
Forum: Wireless/RF
Topic: Soldering RN-41
Replies: 1
Views: 903

Soldering RN-41

Any tips on soldering an RN41 to a PCB? I have one connected on a protoboard with point-to-point wiring dead bug style but I just finished laying out a PC board for the design. I'm planning on using the skillet method of SMT reflow with the module. It works fine for smaller components but I"m a bit ...
by lyndon
Tue Jul 22, 2008 9:47 am
Forum: SparkFun Product Questions
Topic: Wind power for a small MCU board
Replies: 17
Views: 3052

I'd think that a mechanical device like the windmill would be even less reliable than batteries in that cold. Wires become brittle, need cold-rated lubricants, drifting snow to clog up mechanisms, etc... I looked into low temperature batteries before (I live in Minnesota and it drops to about -25F a...
by lyndon
Fri Jul 18, 2008 5:48 am
Forum: SparkFun Product Questions
Topic: battery "gas gauge"
Replies: 4
Views: 2314

As bigglez said, there is no simple, accurate way other than a gas gauge IC and as far as I know, even those aren't very accurate because battery characteristics change over time. A simple, not very accurate way is to monitor the no-load voltage of the battery. Perhaps a comparator set to a voltage ...
by lyndon
Thu Jul 17, 2008 7:03 pm
Forum: SparkFun Product Questions
Topic: low cost DC water pump
Replies: 39
Views: 17938

You can find battery powered (DC) aquarium pumps in most pet stores. I have one around here somewhere. Cost is about $10 or so.