Following on as part of this remote "monitor" gadgets I’m playing with, it would be good to use a single cell (battery) to power the remote devices. In the past some cool step-up devices form Pololu Robotics & Electronics: NCP1402 and S7V7F5 (both shown below).
These allow using a single AA or AAA battery to power +5V devices and fit within the regular footprint of a TO-220 regulator. But I also must include with them the case to hold the AA or AAA battery. So upon further research I found a really neat reference design from Microchip using their MCP1640: MCP1640 Single Quadruple-A Battery Boost Converter Reference Design.
That is so simple, small, and elegant; I figured I had to give that a try. Now I don’t use AAAA-size batteries, but if they did such cool stuff with a smaller size (and packed more complexity), I had to be able to
As part of this concept I’m working on to “monitor” several gadgets remotely using the home router and some sort of wireless “gadgets”, I settled for 433MHz devices. I had some OOK receivers and transmitters which I used in the past, so I decided to start with those.
These are basic ones from either Radiotronix (now Linx Technologies), Wenshing (through Sparkfun), or Laipac. For reference, these are the modules I’ve worked with; but pretty much any standard OOK (or ASK) module should work.
• RCR-433-RP (Radiotronix)
• RCT-433-AS (Radiotronix)
• RWS-371 (Wenshing)
• TWS-BS (Wenshing)
• RLP 434A (Laipac)
• TLP 434A (Laipac)
To use them you modulate the data input with a TTL
So I’ve played now with the WIZ110SR module on and off for a while. What have I learned so far. I unsuccessfully tried to upgrade firmware, and although I followed (or I like to believe I did) the instructions faithfully, I ended up with a brick at the very end. Nothing, the module would do nothing. It would happily draw power, but would not do a thing. Manufacturer recommended shorting the pads for SW1 (this is a switch for which the pads are already on the PCB, but is not populated), this would force a factory reset. Although an interesting approach, and probably useful in countless other times, it had no effect for this issue. Thankfully, Sparkfun gladly exchange the module for me and provided me a working one (they’re awesome that way). Out of this I learned three things: (1) why mess with updating the firmware if the previous one was working, (2) there is a nifty reset switch which may return me back to factory configuration if I mess up too bad (just don’t expect recovery from
Continuing on this topic; last time I included simple code for the PING sensor. Here I present equally simple code for the HC-SR04.
The hookup is pretty simple. Connect two I/Os from the PIC to the HC-SR04 I/Os. The code provides the following: (1) a 10us pulse output to the TRIG input of the sensor, (2) allows for "dead/wait" time, (3) measures the pulse width of the return pulse from the ECHO output of the sensor, and (4) converts this pulse width into distance.
I can confirm that the HC-SR4 (similar to the PING) does not operate at +3.3V; not a big issue, just something to keep in mind when working with these sensors.
Below is tested code used (using PIC12F683) for the PING sensor. The PC was used to read the returns. One observation about this sensor; the HC-SR04 appears (on first look) to provide a some first order filtering to the results (or otherwise be a little more directional) as compared to the PING. This is based on initial results which
This topic has probably been discussed extensively, but every now and then you still see questions about how to use ultrasound distance sensors. So why the post; it's been a while since my last post and I recently order a batch of HC-SR04, so I needed to get ready to play with those.
The HC-SR04 is a cheap copy of the PING sensor. I've used the PING in numerous occasions, and I've built my own as well. But no matter how much more I tried to lower the cost of the one I built, I could never approach the cost of this HC-SR04. So I decided to order a few and try them out.
First of: how do these work. These sensors work on the SONAR principle. A sound-wave is transmitted; if the wave hits something it will return back (think a tennis ball hitting a wall). The longer (time) it takes the sound-wave to come back, the longer distance it had to travel. That is the concept in a nutshell. There are lots more to consider (e.g. type of material the sound-wave reflects back
I’ve been meaning to work with the DS18B20 1Wire device from Maxim for a while now. During an information exchange with a fellow user on the forum on reading multiple DS18B20s I decided to take the plunge. I ordered 10 devices from some “reputable” far east vendor on eBay. The parts (along with some much needed relays) came in a short 10days.
Parts came in right before the Thanksgiving holiday (what a break). What are we supposed to do but give them a try. I checked each of them and all seem to operate ok. To address multiple 1Wire DS18B20 devices using an MCU a few options are available:
• connect each device to individual pins on the MCU,
• connect all devices to one pin through a multiplexer (two or more extra MCU pins are required for addressing),
• connect all devices to one pin an address each through 1Wire commands.
To address all DS18B20 using the same MCU pin, I followed the guidelines from Reynolds Electronics to read
Been meaning to do an article on documenting a class-A amplifier design for a while now. Recently uploaded new article on this topic: Design of a VHF Class-A Amplifier for Optimum Power Output.
The article uses a BFR92A bipolar transistor to create a class-A VHF amplifier. The intent is to provide as much linear output power as possible, while providing match at input and output to provide good tradeoff between efficiency and linearity (i.e. distortion).
For the particular example; the first-order optimum load is 500-ohms. The following plots show the results obtained. The amplifier design (operating from 150-160MHz) shows good efficiency and improves the linearity (i.e. distortion), as compared to the unmatched amplifier case.
10-output power and efficiency.PNG
11-output power and distortion.PNG
Well, the first tagger is built. Wow, I have much more appreciation for these littler guys.
It's still in works. Currently having the following issues:
> internal pull-ups - sometimes they seem to work, sometimes they not
> IR drive level on the transmitter seems lower than original breadboard - need to look at supply voltage and current limiting resistor
Things that could be better:
> there is audio feedback for receiver (when gun is tagged), audio could be cooler
> would be cool to have audio feedback during transmission (i.e. when gun fires) - the transmitter is already set for this, and the receiver has the I/O necessary; need to modify receiver code
> the tactile feedback for the trigger could be better - right now the feedback is provided by a pushbutton switch (it's ok, but doesn't have the cool spring/recoil to it).
> more lights - the LEDs currently in there are hard to see
Boards were received from OshPark/DorkbotPDX - whole process took a 16d, right on time. The new ordering site is super cool.
After assembly and quick checks I found a few errors (of course). A cut and jump on the transmitter was needed; and two cuts and two jumps needed on the receiver.
boards_top side.JPGboards_bot side.JPG
Added some code and got some quick results with the first prototype.
Code ran good; was able to discriminate between Team Selections for both the transmit and receive side.
Now to fit it into an actual gun frame - currently looking at a NERF frame.
I've mentioned these guys before; but I figure to give them another plug here since I've used their service three times now with nothing but good things. I'm talking about DorkbotPDX PCB service; now offering the service through OSH Park (with a cooler interface).
The service is pretty simple. They give you three (individual) boards of the same design for $5/sq-in (so it's really $1.67/sq-in). No setup fee, no shipping charges (in the US). They advertise the boards will ship in 14days from the date the order is acknowledged (i.e. received and payed for). So far the three orders I've place have taken 14d, 15d, and 15d (plus 2d for shipping). Not bad.
I've used ExpressPCB, BatchPCB, and now DorkbotPDX/OshPark.
I prefer this for quick turn-around boards. The cost for the basic (no silkscreen, no soldermask) is about $2.14/sq-in; but you have to buy three boards of 3.8in x 2.5in each. I try to pack more than one design on the board