Sending iR codes from an iRobot Create

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npropanol
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Sending iR codes from an iRobot Create

Post by npropanol » Wed Apr 03, 2019 10:04 am

I am trying to send ir commands from an iRobot Create (original) to control other roombas. The manual contains a simple circuit for sending the ir commands from a dedicated pin, which works as is, but it has an extremely limited range. The excerpt from the manual is here:
Create Open Interface_Page_11.jpg
I would like to use my new SendIR module to increase the range of the signal, but the flow of this circuit seems to me to be going in the wrong direction. Any guidance is most appreciated.
Thanks!

-npropanol
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AnalysIR
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Re: Sending iR codes from an iRobot Create

Post by AnalysIR » Wed Apr 03, 2019 12:14 pm

Based on what you have posted...you will need to invert the signal coming from the LD1 pin/connector(?)

something like this should do:
inverter.png
T1 is an NPN transistor like 2N2222 or any generic NPN transistor should do.
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npropanol
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Re: Sending iR codes from an iRobot Create

Post by npropanol » Thu Apr 04, 2019 12:41 am

Thanks for your reply. That is exactly what I thought.
Just to be clear, the bottom three are ground, right?
Did you mean to say Vout at the top or Vin?
If I connect the Vout to the 5v on the SendIR I get nothing.
If I connect the Vout to 5V then the SendIR just stays on.

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Re: Sending iR codes from an iRobot Create

Post by AnalysIR » Thu Apr 04, 2019 12:15 pm

First of all, I am not familiar with iRobot. I am assuming the circuit you posted is from the iRobot.
Maybe post some photos of your setup , including the iRobot & if there is a standalone IR emitter/remote?

For now I will assume the circuit you posted is from the iRobot itself.
Just to be clear, the bottom three are ground, right?
yes
Did you mean to say Vout at the top or Vin?
vout should be connected to 5V from the iRobot,if available
If I connect the Vout to the 5v on the SendIR I get nothing.
5v, GND and LD1 should be connected between iRobot & SendIR.
If I connect the Vout to 5V then the SendIR just stays on.
post a photo clearly showing the wiring

Finally, I am not sure as to the function of the 100R resistor. It seems unusual...any idea?
It looks like it may be a signal to let the iRobot know an ir emitter is connected.
if so, LD1 should be connected to 'from LD1' point.
'To SendIR' should be connected to either of the 'IR-Tx' pins on SendIR

PS: '1->4K7' on the circuit...should read '1K->4K7'

npropanol
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Re: Sending iR codes from an iRobot Create

Post by npropanol » Fri Apr 05, 2019 6:50 am

First thanks again for your help.
A little background info - iRobot manufactures the Roomba vacuuming "robot" - in 2007 they removed all of the vacuum parts and released the "Create" for robotic development. It featured access to all of the sensors and functions (minus the vacuuming) and included four digital inputs, an analog input, three digital outputs, three high-current low side driver outputs (useful for driving motors), a charging indicator, a power toggle input, serial Tx and Rx, a 5V reference, battery ground and battery voltage. All these can be accessed through a convenient 25 pin connector. LD1 is low side driver 1 which is pin 23 of the 25 pin connector. The circuit I posted is an example schematic from the "Create" manual. So what I have is a wire coming from pin 23, and a 5v power supply and ground. I have a small IR transmitter (pictured) that works with limited range. Normally, (with an arduino for instance) I connect the signal line to DAT and the ground to GND (the VCC is not physically connected to anything on the sensor, so it is not used). If I connect it this way on the "Create" the light just stays on. For it to work on the "Create" I have to connect 5v to the DAT pin and the signal (LD1) to GND.
IR.jpg
As I understand it the 100 ohm parallel resistor is reducing the current draw while not reducing the voltage?
Or to reduce output voltage at no load?
FWIW it works without it.

What about using a PNP transistor instead?

Thanks again!
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Re: Sending iR codes from an iRobot Create

Post by AnalysIR » Fri Apr 05, 2019 10:42 am

OK. All seems as expected. The circuit above should(?) work, if placed between the iRobot & SendIR.

Please upload a photo clearly showing the wiring with the connector, SendIR & the NPN circuit above.

You say it works without the 100R resistor (but try with it out and in... i.e. connected between 5V & LD1)

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Re: Sending iR codes from an iRobot Create

Post by AnalysIR » Sat Apr 06, 2019 2:04 pm

I found a copy of the iRobot create online..and it seems LD1 can take up to 0.5Amps
(please verify that first to avoid damage, as SendIR can draw up to 350mA at full power setting using both jumpers).

If this is the case then the solution may be much simpler..(not as designed, but should work...TBC)

Forget about the NPN circuit above.
Connect 5V & IR-Tx on the sendIR together. (you can use the jumper beside the IR LEDs for that, as it is unused for 5V operation)
Connect 5V from the iRobot to 5V on SendIR. (You can use the spare header pins for that.)
Connect LD1 to GND on SendIR (based on my brief review this should work)

Note: I have not tested this so please review & confirm everything as you proceed to avoid damage.

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