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Re: Accurate 0.1 water level sensor

 by MichaelN ¦  Tue Apr 05, 2016 9:32 pm ¦  Forum: Projects ¦  Topic: Accurate 0.1 water level sensor ¦  Replies: 4 ¦  Views: 735

Your requirement for 0.1mm resolution will be a real challenge. What's the maximum depth of water? Have a look at the following, but note that with the specified sensor and schematic the resolution would be worse than 4mm, when using an Arduino operating from 5V.

Re: Parts procurement..

 by MichaelN ¦  Tue Apr 05, 2016 9:01 pm ¦  Forum: Projects ¦  Topic: Parts procurement.. ¦  Replies: 4 ¦  Views: 478

I assume you're in USA? We're spoiled in Australia, where we get free next-day delivery from RS (no minimum order) and Element14 (minimum $AU45 for free shipping).

Their USA branch companies (Allied & Newark) don't offer free shipping it seems.

Re: Oscilloscope recommendations?

 by MichaelN ¦  Sat Apr 02, 2016 3:11 pm ¦  Forum: Forum ¦  Topic: Oscilloscope recommendations? ¦  Replies: 17 ¦  Views: 9378

I spent the 130 for the usb one for now as it meets my immediate needs. I have a feeling I'll End up with a fancier one down the road once I get more and more into building with arduino and circuits Don't listen to the nay-sayers - a USB scope is VERY useful, and I prefer them over benchtop units i...

Re: Power supply conditioning...?

 by MichaelN ¦  Tue Feb 11, 2014 5:48 am ¦  Forum: PCB Design Questions ¦  Topic: Power supply conditioning...? ¦  Replies: 20 ¦  Views: 8345

Rds(on) is not important for me because i will not use battery for Vin. Important is to have the lowest voltage drop possible because the board control dc motors that are rated for 12vdc The voltage drop is directly related to Rds(on), as the MOSFET behaves like a low-value resistor. I want to know...

Re: Mixed signal AGND DNGD separation sugerencies

 by MichaelN ¦  Sun Feb 09, 2014 4:42 am ¦  Forum: PCB Design Questions ¦  Topic: Mixed signal AGND DNGD separation sugerencies ¦  Replies: 1 ¦  Views: 696

...I don't have any idea of what ground plane put under this cross section, an Analog Ground plane or an Digital Ground plane. Those articles are good; as per the first one, you should only have ONE continuous, unbroken groundplane (ie, no split planes), so the question of analog or digital ground ...

Re: Li-Po inductive charging

 by MichaelN ¦  Fri Feb 07, 2014 5:01 am ¦  Forum: Projects ¦  Topic: Li-Po inductive charging ¦  Replies: 6 ¦  Views: 3516

For a hobbyist forum I believe that is best to give good advice, rather than suggest an approach that is possible -- if you know what you are doing. For this reason, I recommend that LiPo or Li-ion batteries be charged out of circuit, with a charge controller that is designed for the task. I think ...

Re: MicroUSB LiPo charger, or breakout board and a resistor

 by MichaelN ¦  Thu Feb 06, 2014 9:25 am ¦  Forum: SparkFun Product Questions ¦  Topic: MicroUSB LiPo charger, or breakout board and a resistor ¦  Replies: 2 ¦  Views: 557

I know that the lipo charger has an IC built in to protect the battery and limit current, but isn't that the point of the protection circuit built into the lipo battery? The protection IC built into the battery is really designed to stop anything really nasty happening - it's not designed to ensure...

Re: Li-Po inductive charging

 by MichaelN ¦  Thu Feb 06, 2014 9:15 am ¦  Forum: Projects ¦  Topic: Li-Po inductive charging ¦  Replies: 6 ¦  Views: 3516

jremington wrote:...They can be charged in place, but you must have a switch or some other way to isolate the battery, so that the charge controller is not misled.
I don't think this is really necessary, especially if the drone isn't itself using much power during charging.

Re: Power supply interference causing glitches?

 by MichaelN ¦  Tue Feb 04, 2014 6:23 am ¦  Forum: Arduino ¦  Topic: Power supply interference causing glitches? ¦  Replies: 6 ¦  Views: 1243

The sensor is a Digital Temperature and Humidity sensor (SEN0148). It's wired like it shows on the wiki page, except without the resistor. Try adding the resistor - pullu...

Re: Who sells small LiFePO4 batteries?

 by MichaelN ¦  Sat Feb 01, 2014 10:45 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Who sells small LiFePO4 batteries? ¦  Replies: 3 ¦  Views: 1273

MichaelN wrote:Hobbyking is normally my go-to place for this type of thing...
Hmm, this seems to be the smallest they have in LiFePO4: ... _Pack.html

Re: Vacuum pump

 by MichaelN ¦  Sat Feb 01, 2014 10:42 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Vacuum pump ¦  Replies: 14 ¦  Views: 1723

Here is a good tutorial and wire diagram, You could use a different N-channel MOSFET, just make sure it's rated for your pump motor. You also want to make sure the MOSFET is rated for logic-level (5V) gate drive. Most are, but some like 10V or more on t...

Re: Stolen bikes

 by MichaelN ¦  Sat Feb 01, 2014 7:06 pm ¦  Forum: GPS ¦  Topic: Stolen bikes ¦  Replies: 4 ¦  Views: 2193

stevech wrote:But! You have to pay the monthly cellular fee.(e.g., first year)
Really? In Australia there are $0 /month cellular plans where you just pay for data / calls / messages. As long as you're not constantly tracking (no point when the bike isn't stolen), the cost would be next-to-nothing...

Re: Who sells small LiFePO4 batteries?

 by MichaelN ¦  Sat Feb 01, 2014 4:56 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Who sells small LiFePO4 batteries? ¦  Replies: 3 ¦  Views: 1273

Hobbyking is normally my go-to place for this type of thing, but I can't see what size cells they have as their servers are down :(

Does it need to be LiFePO4? Lipo would give you far more options...

Re: Freelance PCB design needed

 by MichaelN ¦  Sat Feb 01, 2014 4:52 pm ¦  Forum: PCB Design Questions ¦  Topic: Freelance PCB design needed ¦  Replies: 1 ¦  Views: 735

Unfortunately I don't have time myself, but a few things a potential contractor will need to know: - Do you have a schematic, or at least more detail of how you want things connected? How are the sensors connected, and what will the power supply look like? Eg, a small solar panel charging a lithium ...

Re: Vacuum pump

 by MichaelN ¦  Sat Feb 01, 2014 4:40 pm ¦  Forum: SparkFun Product Questions ¦  Topic: Vacuum pump ¦  Replies: 14 ¦  Views: 1723

That looks like a standard brushed-DC motor, and PWM (Pulse-Width-Modulation) is a better way of controlling speed than just reducing the voltage. Just pick your favorite microcontroller (eg Arduino), add a MOSFET and diode (to prevent back EMF voltage spikes) and you should be all set (after writin...

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