Power

[pyrhho]

This may be a dumb question, but the standard arduino mini hasa +5v and +9v power input. The Yellowjacket has only a "VCC" in, I'm assuming this is +5V? or would +9V work there? I'd like to power it from a 9V battery, but don't want to explode it!

Thanks!

[SirPoonga]

The VCC pin looks like it is directly connected to the 5V pin. It is part of the TTL header so it really wouldn't be used as an input. It is providing power to the TTL interface - i.e. usb->ttl converter.

[pyrhho]

The VCC pin looks like it is directly connected to the 5V pin. It is part of the TTL header so it really wouldn't be used as an input. It is providing power to the TTL interface - i.e. usb->ttl converter.

Ok, so the VCC is used to power the usb breakout stuff. So.... how does one power the yellowjacket then?? sorry, I am a bit new to the hardware side of things.

Thanks!

[SirPoonga]

Probably just a 5V source to the 5V pin or 3.3V to the 3.3V pin. I am going to guess U2 or U3 in that pic is a voltage regulator to drop the 5V down to 3.3v. The question then is what voltage regulator is it? Can it handle more than 5V? Probably not since it is passing that to the breakout.

If it has to be 5V you will need to create your own power circuit. A 7805 voltage regulator (very common, Radioshack even has these) would work. Look up schematics online on how to use. I'm going to be trying this out.

Don't worry, I'm not a hardware guy either. Some stuff I have learned the hard way Nothing like frying three TLC5947 chips accidentally and seeing the magic smoke appear

[cbenedict]

Power is supplied to the board at the RAW and GND pins. There are two voltage regulators on the board...one for the ZeroG module at 3.3V, and one for the AVR at 5V. Why Async did a split power supply is a question mark. Be careful sinking current from the 3.3 and 5V pins...the onboard regulator can only source 250mA of current (and that might be with a heat sink...I'd have to study the datasheet more carefully...the reg is not heat sinked on the Wishield). The ZeroG module itself (depending on its transmit mode) can use up to 230mA according to the datasheet.

[mfm219]

Since I wanted to get my yellowjacket going and there have been a lot of posts about powering it, I did a little digging into powering it from the RAW pin.

As listed on the schematic, the RAW pin is the input to a 5V regulator (Micrel MIC5129-5.0BM5, package SOT-23-5, marking LG50). The 3.3V regulator (Microchip MCP1703) is supplied from the output of the 5V regulator. Looking over the datasheet for the MIC5219 (http://www.micrel.com/page.do?page=prod ... 5219.shtml), the maximum power dissipation is limited to about 0.5-0.6W when operating at 25C. I did not research the MCP1703 since it is working off a controlled input voltage and figured asynclabs spec'ed it properly.

I measured the power draw of the yellowjacket and got these numbers: 35mA with the Wifi chip disabled, 120mA with the Wifi chip enabled and connected. These are average numbers from a hand multimeter with the device powered using a 6V supply. The ZeroG datasheet says the Wifi chip draws around 85mA with Rx on - which agrees with the measurements. Tx active can increase the instantaneous power draw significantly (165-230mA depending on the wifi transmit power).

The MIC5219 datasheet has equations and charts for figuring out the max voltage drop for a given current draw. Based on a continuous current draw of 120mA, the maximum input voltage on the regulator (RAW pin) is 9.5V. So, not a surprise that 12V on the RAW pin could cause some problems as other posts have reported. But, even ~9V doesn't give any margin for transmitting or other components being powered off of the Vcc pin of the board. Increasing the average current draw to 250mA, the max input voltage is 7.2V.

So, the safe voltage to use on the RAW pin depends on what you are doing. Seems like <7.5V is plenty conservative. I am currently using a 6V supply that I had laying around. There are battery options in this range too. So, I will probably stick down <7.5V to stay out of trouble.

[John_Ryan]

So, the safe voltage to use on the RAW pin depends on what you are doing. Seems like <7.5V is plenty conservative. I am currently using a 6V supply that I had laying around. There are battery options in this range too. So, I will probably stick down <7.5V to stay out of trouble.

Good job! 5 volts it is = )

I wish they'd document the YJ properly, this question is likely to get asked every time someone new buys one.

[GregEigsti]

Thanks mfm219!!!

I wish they'd document the YJ properly, this question is likely to get asked every time someone new buys one.

Agreed - as well as the other pins (SPI, etc.). I'm assuming that the YJ pinout matches the WiShield pinout but it would be nice to know for sure.

Based upon other comments and a quick look at the schematic I am guessing that the following is kosher. I am getting ready to make first use of my YJ as an add-on to an existing circuit which has regulated +3.3v available. If I connect the +3.3v pin of the YJ to the existing circuit's +3.3v is that going to be ok? I assume that it will be and will study the schematic and parts first. Does this sound kosher to those of you who have used your YJs (or who understand electronics/electricity better than I)? Are there implications to providing +3.3v through the "back door"? Will this negatively affect the +5v regulator on the YJ?

My plan for global domination is to connect the YJ to the Mattel Mindflex headset thereby making its "brain activity" data available on the net - probably UDP broadcast. I think it would be kind of neat to gather the "brain activity" data coming out of the headset and make use of it - somehow - or even just display it while completing different tasks... The next step will be world domination via thought transmission - I'm gonna have to amp that sucker up to reach NZ

Interestingly the rest of the family's Mindflex control abilities are pretty much hit and miss - except for my son who can make the ball go up and down at will. I think I shall rename him "Retirement Plan"!

Thanks all!
Greg

[seanblink]

Please hook it up to Twitter.

[mfm219]

Greg - I would not connect the 3.3V supplies together. Just connect the grounds. You can put some regulators in parallel, but they have to be designed for it and some extra components are needed. Otherwise, one will take all the load until it droops and the other kicks in. This means one has to be overloaded to get the benefit of the second.

By the way, I checked the 3.3V MCP1703 regulator. It is well matched for the ZeroG wifi chip as you might expect. It has a little bit of head room depending on the operating conditions. So, it could source a few 10's mA to some extras if needed. But, again it depends on overall operating conditions (temperature, duty cycle for Tx of wifi, etc).