Search found 1191 matches

by MichaelN
Wed Mar 27, 2013 7:52 pm
Forum: SparkFun Product Questions
Topic: General Design Questions for a Widget
Replies: 15
Views: 1127

Re: General Design Questions for a Widget

I too worry that you’ll release the “magic smoke” with your proposed scheme. Also, as Mac points out you’d need 4 of your relays to build a H-bridge. If all you want is forward-off-reverse control, I suggest you use old-fashioned DPDT relay to reverse the polarity of the voltage sent to the motor. T...
by MichaelN
Mon Mar 25, 2013 6:32 pm
Forum: Arduino
Topic: Arming ESC with Arduino Uno
Replies: 14
Views: 13460

Re: Arming ESC with Arduino Uno

Standard RC signals are a pulse between 1 and 2 milliseconds wide, every 20 milliseconds. To arm the ESC you need to provide 1ms wide pulses, which equates to minimum speed (2ms equates to maximum speed). The number of required pulses is unknown, but I’d suggest 10 to 50 pulses should work. Do you h...
by MichaelN
Mon Mar 25, 2013 12:32 am
Forum: SparkFun Product Questions
Topic: USB Hub on a chip?
Replies: 4
Views: 2247

Re: USB Hub on a chip?

You should be fine using one of these chips by just using the manufacturer's reference designs. Make sure you follow any recommendations for board layout etc, as there are high frequencies involved.
by MichaelN
Thu Mar 21, 2013 11:50 pm
Forum: SparkFun Product Questions
Topic: Advice for hydraulic master thesis.
Replies: 7
Views: 759

Re: Advice for hydraulic master thesis.

Yep, the Atmel-based Arduino probably isn't what you want. If you like Arduino, have a look at the Arduino Due, which uses a 32-bit Arm chip. Otherwise, a DSP is probably better for doing high-speed analog measurements and calculations. Maybe something from TI's "Picollo" range eg the 28027. This ca...
by MichaelN
Thu Mar 21, 2013 8:06 pm
Forum: SparkFun Product Questions
Topic: Op amp question driving flexiforce load sensor
Replies: 12
Views: 2441

Re: Op amp question driving flexiforce load sensor

And my thought was that the Vt (in the Vt-1v) might be some "threshold voltage" and that Vt would be applied, as above, to the op-amp + input. But they show it connected to ground. If there was a bipolar supply available, then why not run the op-amp off of it ? I agree it is odd, but the circuit as...
by MichaelN
Thu Mar 21, 2013 6:46 pm
Forum: SparkFun Product Questions
Topic: Op amp question driving flexiforce load sensor
Replies: 12
Views: 2441

Re: Op amp question driving flexiforce load sensor

The circuit you've linked to makes no sense to me. It's an inverting op-amp which means, with a 5v unipolar supply, the input voltage needs to be negative to work. Note the -1V supply connected to the flex sensor - that's what allows this to work. If a negative supply voltage isn't available, there...
by MichaelN
Tue Mar 19, 2013 5:36 pm
Forum: SparkFun Product Questions
Topic: Dog Camera
Replies: 4
Views: 509

Re: Dog Camera

Do you want to do this for the challenge, or do you just want a functional system? If it’s the latter, I’d suggest a pre-built system, including cameras(s) and HDD recording box. They are available very cheap (even Ebay can be OK), and you probably won’t need the PIR motion sensor. These days the re...
by MichaelN
Tue Mar 19, 2013 12:24 am
Forum: BatchPCB
Topic: PCI card fab question
Replies: 3
Views: 3801

Re: PCI card fab question

You won't be able to get any of the low-cost PCB suppliers to make that type of board. Just wondering what the limiting factors are with BatchPCB? They can route complicated shapes, so they should be able to make the board with the required slot. Not sure about BatchPCP, but you can add gold (ENIG)...
by MichaelN
Sun Mar 17, 2013 7:37 pm
Forum: PCB Design Questions
Topic: Silkscreen limits?
Replies: 5
Views: 871

Re: Silkscreen limits?

I assume you're talking about BatchPCB? They use Goldphoenix, who I have used several times in the past. I have used text that size without issue, but I wouldn't go any smaller.
by MichaelN
Thu Mar 14, 2013 5:45 am
Forum: SparkFun Product Questions
Topic: Help with power control
Replies: 2
Views: 338

Re: Help with power control

by MichaelN
Tue Mar 12, 2013 9:50 pm
Forum: New Product Ideas
Topic: how about a hearing aid kit ?
Replies: 4
Views: 1813

Re: how about a hearing aid kit ?

what do you think of the clones on chinabay ? Not sure - I'd check more relevant forums to see what people recommend. #who makes the chips in the devices that costs $1000s ? surely theres a massive markup here . and why cant they be cloned ? Proprietary chips are expensive since the development cos...
by MichaelN
Mon Mar 11, 2013 9:44 pm
Forum: BatchPCB
Topic: 0.02" Drill Size
Replies: 11
Views: 5540

Re: 0.02" Drill Size

The main thing that concerns me is that it failed the Eagle DRC because of the drill size. It passed BatchPCB's DRC bot however, so just to try it out, I changed a via on the board to 10mil and submitted the board and it still passed the BatchPCB DRC, so I am guessing there is not something complet...
by MichaelN
Mon Mar 11, 2013 7:28 pm
Forum: SparkFun Product Questions
Topic: weatherproofing an ultrasonic sensor
Replies: 5
Views: 1837

Re: weatherproofing an ultrasonic sensor

I really think you should use proper waterproof ultrasonic sensors. $89 for the Maxbotix sensors doesn't sound too bad to me. If you're on a really tight budget you could make something using sensors such as the T/R40-16B transducer from the Chinese manufacturer Audiowell (available from Jaycar in A...
by MichaelN
Mon Mar 11, 2013 7:23 pm
Forum: SparkFun Product Questions
Topic: Help with power control
Replies: 2
Views: 338

Re: Help with power control

Due to the type of LiPo, charging while drawing a current is bad for the battery. Why is that? I don't think it will be an issue unless the power draw by the circuit is high compared to the battery capacity / charge currrent. If it was me, I'd just get a cheap pre-built LiPo battery charger (eg fro...
by MichaelN
Mon Mar 11, 2013 5:46 pm
Forum: Wireless/RF
Topic: XBee range improved if only one radio is xbee Pro?
Replies: 3
Views: 563

Re: XBee range improved if only one radio is xbee Pro?

There can be benefits of doing this, depending on the antennas you use. If you use the same antennas at each end, I can't see a benefit (I think the receive sensitivity is similar for both XBee models?). You need to do a link budget to see how the numbers come out. Compare this to what NASA does wit...