I am using a Picaxe 28x1, and AXE020 project board and a TSOP38238 IR Receiver
I have recently completed my version of the Start Here Robot, and want to upgrade it so that I can remote control it. Instead of spending £10+ on the kit from picaxe direct, I have dug out an old all-in-one remote, and ordered a TSOP38238 IR Receiver from Ebay (clicky for datasheet, see also application overview) but I am a little bit confused over how to connect it up and am hoping someone with greater knowledge can help me in my noobiness :)
The picaxe ir upgrade kit describes connecting everything upto the IR Area on the AXE020, but am I correct in thinking that I can connect the pins to any V+, GND and digital input pin?
According to the datasheet for the TSOP38238, I need a resistor between the V+ pin on the board and the V+ pin on the component, and a capacitor between V+ and GND, HOWEVER, it states that "R1 and C1 are recommended for protection against EOS. Components should be in the range of 33 Ω < R1 < 1 kΩ, and C1 > 0.1 µF". EOS I have discovered is Electrical Over Stress, IE too much power, but since the component is rated upto 6V, and I am using 3 x AA(non rechargeable) batteries @ max 4.5V I think I dont need them? Is that correct?
The googling I have done has come up with this tutorial (for arduino) and this product page on adafruit using the exact same IR Receiver as me, wiring directly to the board etc with no resistors, capacitors etc, but other posts I have seen say otherwise......I want to be sure before I connect everything up so that I dont fry anything!
I have a similar sensor from the local electronics store ( not Vishay, though ). I just plugged mine into the breadboard, and nothing bad happened. The schematic looks like it is just a filtering circuit ( R/C from Vcc to Gnd ). The current draw is minimal ( < 3 mA ), so you could probably even power it from the Picaxe’s I/O pins.
I’d recommend you program the universal remote for Sony codes instead of the JVC I used. They look much easier to deal with. Here’s some starter info on Sony protocols: http://www.ustr.net/infrared/sony.shtml
Most datasheets recommend those parts be added to reduce noise. That is variations in readings producing inaccuracies. Although you can deal with it in code as well I think if your hardware design is robust then coding is easier. I have found that they do indeed do what the datasheet suggests.
Thanks - the datasheet says that the component is “insensitive to supply voltage ripple and noise” so i figure that it shouldnt be a problem. I was more worried about frying the sensor. If I have troubles then I will connect up a resistor and capacitor.
Thanks, good to hear that you have connected a similar sensor up directly without frying it! Although, there are always differences between different components, I think this one seems pretty resilient
From the research I have done, its best to use Sony codes as they pulse at a lower rate so the Picaxe can decode them easier.
The Sony codes have a much clearer dlineation between marks and spaces than other codes I’ve seen. The JVC codes required my controller to sample in the middle of each pulse and “time-out” at a mark or space.
Merser put it much better than I did. Small capacitors and low value resistors wired like this typically provide noise reduction. Current spikes, more than voltage ( unless it’s really big ) are more likely to cause problems. A resistor and a cap in this configuration won’t save you!
The really great thing about these sensors is their near immunity to interference. Natural IR and even artificial IR shone right at them doesn’t mess them up. They only pay attention to IR in their frequency range ( 38 kHz in the case of yours ).
