Previously I made a ATtiny GPS Long Lat logger to record the GPS co-ordinates to an EEPROM and now it’s time to implement the full functionality of my project which is to check an accelerometer for motion, monitor the GPS until we are in a certain area and then send an SMS. If it’s a few KM away from the area, then it’ll turn the GPS off for a few minutes and check again later but if it’s close to the area, it will keep checking the GPS as long as movement is detected within 1 minute.
https://www.youtube.com/watch?v=JNAqu732Uqw
I was using the ATtiny2313 before however it didn’t have any ADCs so I’ve switched to the ATmega88 which is approximately the same price. To reduce power I have a mosfet for the accelerometer, GPS and mobile phone. The mobile I’m using this time is the Nokia 3210 which cost me $22 from Ebay, the battery seemed to discharge after a couple of days so I was trying out different options.
// Reset PC6 1|o |28 PC5 N Mosfet for MMA7361 accelerometer
// RX GPS PD0 2| |27 PC4 N Mosfet for GPS
// TX SMS PD1 3| |26 PC3 N Mosfet for Nokia 3120
// PD2 4| |25 PC2 X Axis
// PD3 5| |24 PC1 Y Axis
// PD4 6| |23 PC0 Z Axis
// VCC 7| |22 GND
// GND 8| |21 AREF
// XTAL PB6 9| |20 AVCC
// XTAL PB7 10| |19 PB5 SCK
// PD5 11| |18 PB4 MISO
// PD6 12| |17 PB3 MOSI
// PD7 13| |16 PB2 Optoisolator for Nokia 3120 power button
// PB0 14| |15 PB1 LED
The Nokia 3210 seems to power up from ~2.3V to 3.4V, so one option is to try a 3.7V Li-ion with a diode to drop it however after some experimentation it switches only stays on for a few seconds.
A little while ago I had a Netgear ReadyNAS unit which was faulty and wasn’t able to repair it however I thought it would be worth re-using the case to make my own NAS using the Raspberry Pi. I decided to build my own SMPS to provide 5V and 12V to the drives and the Pi and I’m using USB hub with 4x USB to SATA adapters to connect to the 4 hard drives.
https://www.youtube.com/watch?v=-9CjN0F9VXo
(how it all looks at the moment)
After hooking up an 16×2 LCD display to the Pi, I made a start up script in Python to check the drives, assemble the array, mount it and then display the RAID status and free space (see the video above).
Today we’ll be taking a look at the DrayTek Vigor2710ne Wireless ADSL2+ Router which is fairly recent from 2012, it has the usual 4 10/100 LAN ports and 802.11n Wifi capability.
One screw later and we’re in.
Most capacitors on the board are branded Su’sucon which may not be the one of the good capacitor brands. The board has the option of fairly large capacitors which aren’t populated – something seen more in older routers. There’s also a small slot on the PCB which the antenna is wrapped around to keep it in place.
I’ve previously bought an alarm system from Ebay and have been making modifications to it such as making the PIRs wireless and added wireless sirens. On our last part, we added a way to check which sensors have checked in.
By using everything that we’ve built and modified, it’s now time to make our own alarm system. We’ll be adding in our own PIR, Door sensor, making a slight change to the Siren and modifying the Server.
PIR Sensor
I was thinking about how I could potentially box up the PIR with the PCB but I found that the PIR module you buy from Ebay fits in nicely to the existing casing, I removed the PIR cover and it works well. I’ll be switching from the 3V coin cell to a 3.7 Li-poly so that the PIR and the PCB will run off this which should last at least a few years.
One down side of running from the Li-poly battery is that after testing I found that the PIR is unstable when the voltage drops to 3.3V the PIR automatically turns on. One thing I should have added a while ago was a way to monitor the battery voltage, so we’ll add that this time and the cut off will be 3.5V. A few cuts on the PCB, adding some resistors, re-wiring and it’s ready to go.
From our last post we looked at the base configuration of a SMPS using the MC34063. In this part we’ll look at adding in an external transistor so that we can bypass the 1.5A peak current limit present on the MC34063.
Above we have the circuit configuration which we can add our PNP transistor on, I’m using the TIP42C.
(Voltage – blue, Current though diode – green, Current though inductor – red)
We can test this configuration on LTspice, though one problem when using the transistor is that it gets very hot. For testing I’m using two 100 ohm resistors, so it’s quick to switch on and off. We need an inductor and diode that can handle the current because the 1N5819 diode only can do 1.5A so I choose the Toshiba CMS05-TDE which can do 5A and only has a 0.45V voltage drop. I was able to salvage a decent sized inductor from an ATX power supply.
A little while ago I started looking into CPLDs and because you can have things running in parallel, I thought I could use use one to build a logic analyser which saves the sample to external SRAM. At the moment, I still have the Altera MAXII EPM240 development board with an on board 20MHz oscillator.
First things first, it’s time to simulate my implementation of the SPI protocol in Modelsim so we can write to the SRAM and then I could use an AVR to read the location to verify the write. Download cpld_sram_write
In one of my previous posts, I integrated the LM2596 module into my SPPS project, I’ve been trying out a RAID5 array with 4 hard drives attached to my Raspberry Pi and now it’s time to think about how to power it all. Each hard drive takes about 0.7A on the 5V and 12V rail plus about 1-2A for the Pi so 5V @ 5A and 12V @ 3A but the peak current will be a bit higher when all the hard drives start up; I could use a couple of LM2596 modules but I’d rather build my own.
I’ll need something other than the LM2596 that can deliver a bit more power which is where the MC34063 comes along when in the right configuration.
The MC34063 is a buck/boost/inverting switching power supply, you add in a few parts and then it’s good to go. The way a switching power supply works is by using a oscillator at a fixed frequency and a voltage reference with comparator to turn on the mosfet in line with the oscillator when needed, this ensures that the mosfet isn’t fully on all the time.
The current from the mosfet passes through the inductor and when the mosfet turns off, the current passes back through the diode and eventually the inductor will charged up to the voltage we require; and once reached, the mosfet only has to provide short bursts of current to keep the voltage stable – you can see this in action in the above simulation (green is voltage and blue is the current passing through the inductor)
Today we’ll be taking a look at the Cisco Small Business Pro SRP527W ADSL2+ Wireless Router which has 4 LAN ports and 2 phone ports for VOIP. We have taken a look at another Cisco router so I’m expecting to see a few of the same parts.
Four screws later and we’re in.
First off, there are quite a few SMPS (SC4525A) around the board and a few large capacitors too, on the last Cisco router we saw none of these 25V 1500uF capacitors. The Wifi module is much smaller, has a proper u.FL connector and there is attention to detail to keep the Wifi antenna wire in place by having the small plastic holder on top of the LAN ports. There is a 8.192 crystal oscillator on board along with 2x 25MHz and a 64MHz crystal.
I have had a RC car for about 10+ years (15 years old according to the PCB date code) which I think cost $50 at the time and I thought it would be fun to replace the electronic control boards with an AVR and nRF. It used to run on 8AA batteries and the transmitter on a 9V battery. We’ll be having a look at how things were before and how things look now.
(sneak peak of the end result)
Before – Receiver
Here’s how the receiver looked before, lots of analog parts with a few IC parts like the MC14174 flip-flop, MC14024 ripple counter and power transistors on 2 heatsinks.
The left/right control is just a motor with what looks to be some form of feedback (with a few wires coming out of it) so it can detect how far to turn the motor.
AdvanceVGA – Play your GBA on the big screen! Swap out the LCD for our board, solder some wires, connect 5V USB and VGA and you’re ready to go.
GBxCart RW allows you to backup GB/GBC/GBA ROMs, save or restore game saves and re-write supported flash carts. Mini RW option available for GB/GBC only.
Wireless Gameboy Controller – Use your Gameboy, mGB, GBC, GBA, GBA SP, GB Micro, NDS and NDS Lite as a wireless controller on Windows, Linux, Raspberry Pi, etc, and on your NES, SNES, N64, Gamecube and Wii.
