Wireless Remote Control troubleshooting question

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Sparky Williams
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Wireless Remote Control troubleshooting question

Post by Sparky Williams » Fri Feb 27, 2004 4:51 pm

I've built a transmitter and a receiver for a remote control unit featured in a Nuts and Volts article (April 2002), "Build a 418 MHz Wireless Remote Control," and unfortunately can't get it to work. <p>Although the article calls for construction on PC boards, I've constructed the transmitter and reciver on breadboards and do not know whether the transmitter, receiver, or both are not working. The article calls for the receiver to be powered either by AC or 12 volt battery power. I chose battery power (two six volt lithium batteries in series). I am a beginner at this and the only test equipment I have is an inexpensive multimeter. <p>Can anyone out there offer me some practical advice in plain english on how I could go about trying to figure out which unit is not working and how I could test it to isolate the problem? <p>I've tested for continuity, re-examined the connections, verified I have the correct parts, and can't find the problem. I've also soldered the RF modules directly to the PC boards (and their respective capacitors) and connected the boards to their respective breadboards. <p>Any help would be greatly appreciated.

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Edd
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Re: Wireless Remote Control troubleshooting question

Post by Edd » Fri Feb 27, 2004 7:52 pm

Zeek:
I don’t happen to have that issue available here, but I’ll throw two things out.
1 Can you give the model/manufacturer/part number of the T & R modules
so that they might be possibly researched via Web. Possibly, are they Glolab or Radiotronix units ??
2.As of July 2000 this data was current ,when I ran into him at EDN:
<< I can be reached by e-mail at [email protected] J. Caristi>>
Where you will have to make general post to that site and let it filter on down to him…That is…..unless he has job hopped since then.<p>73's de Edd
[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected].........(Firewalled-Spam*Cookies*Crumbs)
;) ;)<p>[ February 27, 2004: Message edited by: Edd Whatley ]</p>

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Chris Smith
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Re: Wireless Remote Control troubleshooting question

Post by Chris Smith » Fri Feb 27, 2004 8:01 pm

Test the transmitter first. Use a hand held AM radio near the transmitter, and tune it to hear a hum, buzz, or whine while the unit is on. Then activate the transmitter and you should hear a click plus some other hash noise. This only proves that the unit is some what working, just not necessarily working properly. Also use an ammeter to see if both have a current draw. Other than this, with out proper equipment, its hard to check why they don’t talk to each other, if they draw power, and sort of work. It could be as simple as they are talking one language [frequency] and hearing another?

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Re: Wireless Remote Control troubleshooting question

Post by Sparky Williams » Fri Feb 27, 2004 9:30 pm

Edd, <p>Both RF modules are made by Linx (tranmitter part no. TXM-418-LC; receiver part no. RXM-418-LC-S). I downloaded and read the tech sheets on both modules, including their pin descriptions, trying to gain any helpful information and was not able to find anything that was helpful to me. <p>As for Mr. Caristi, I did ask him some questions when I wrote to him ordering the PC boards, and he did answer me (I'm currently awaiting another response from him regarding a test reading mentioned in the article), but at this stage in my project I feel like I do not want to burden him too much and am, therefore, reluctant to write him again.

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Re: Wireless Remote Control troubleshooting question

Post by amuron » Fri Feb 27, 2004 9:55 pm

Most likely they are not working as you built them on a breadboard instead of a pcb. I've built a number of projects with Lynx parts. Never had any problem, but every single one was on a pcb.<p>If you look in the Lynx app notes they say "During prototyping, the module should be soldered to a properly laid out circuit board. The use of prototyping or "perf" boards is strongly discouraged."<p>Since you did use a breadboard, did you put a copper ground plane under the chip. You can use copper tape.<p>The same question applies to the antenna lead. Controlled impedance is important, with a bread board, keep it as short as possible.<p>Lsstly, these can be a real pain to solder. You can overheat the chips and as a result cause the modules to fail. My tech did that to me on the first proto a few years ago. Removing the modules is really difficult should you burn one out.<p>Good luck,
Ron

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Edd
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Re: Wireless Remote Control troubleshooting question

Post by Edd » Fri Feb 27, 2004 10:36 pm

Those are quite stable units, looks like they should be foolproof. As far as stability, looks like the xmitter is using a trimmed SWIF filter in its osc design to assure stability. Also the receiver is a quantum leap in its design in using a Swif in its filtering
As well as a full blown superehet in that small package profile. Thanks to technology trickle down from the cell phone industry.
Your units data:
http://www.rfdigital.com/pdf/rfd24005.pdf
RXM-418-LC-S…the Receiver module
http://www.rfdigital.com/pdf/rfd24002.pdf
TXM-418-LC…….the Xmit module<p>Since you are crimped on your test equipment, looks like the very simplest test might just have to do . Start with an initial monitoring of the transmitter and confirm that Pin 2 data input does not have a logic high on it from any attached circuitry, it needs to be low.. Then move over to the receiver and check its Pin 8 and confirm its also at its logic low state. I am unsure if your xmit Vcc supply is operated at its lower limit spec of 3vdc or at the 5vdc level. Whichever , meter pin 8 of the receiver on 5vdc meter scale range via a mini clip and then go over to the xmitter and connect a 1k resistor between its Vcc ( Pin 7) and its data in (Pin 2)
That high level should emit an RFcarrier from your xmit module and you should see a single voltage level shift on your metering on the rec end.
Now if you only had a scope and a pulse generator….oh well…..
If the above checks out , looks like your RF link of the project is working ok.<p>73's de Edd
[email protected] .........(Interstellar~~~~Warp~~~Speed)
[email protected].........(Firewalled-Spam*Cookies*Crumbs)
;) ;)<p>[ February 27, 2004: Message edited by: Edd Whatley ]</p>

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jwax
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Re: Wireless Remote Control troubleshooting question

Post by jwax » Sat Feb 28, 2004 6:07 am

Am I missing something? Both TX and RX are rated for 5 vdc supply maximum!
Using 6 lithiums in series may have cooked them both.

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jwax
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Re: Wireless Remote Control troubleshooting question

Post by jwax » Sat Feb 28, 2004 6:09 am

Rather, using 12 vdc my have fried them.

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Edd
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Re: Wireless Remote Control troubleshooting question

Post by Edd » Sat Feb 28, 2004 1:47 pm

http://www.nutsvolts.com/images/TOC_Pic ... aristi.jpg
Certainly/hopefully the unit was built according to scripture….as above… in which case the DC just steers on thru the FWB and then on into the low power 3 term reg U3…with its reg 5V out feeding the PCB’s circuitry.
73’s de Edd

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Chris Smith
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Re: Wireless Remote Control troubleshooting question

Post by Chris Smith » Sat Feb 28, 2004 7:38 pm

Indeed, if you have used over 5 volts, both are most likely fried.

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Re: Wireless Remote Control troubleshooting question

Post by perfectbite » Sun Feb 29, 2004 1:24 pm

Zeek, I sympathise with you. It seems that quite a few of the N&V projects need expert 'tweaking' to work properly. A while ago I attended a beginner's electronics class (instructor Russ Klien of IUOE Loc. 39 in S.F) and the first thing we built was an ultra simple logic probe. You would laugh if you saw it it is sooooooo simple. It consists of an 8" length of 1/2" plastic corner coving with 45 degree cut on both legs of one end, to the inside corner of the coving was tied two resistors, one GFT 2221A transistor and one red LED. Sticking out at the mitred end of the coving was one wire 'leg' of one of the resistors which was the probe, the other end of that resistor was soldered to the transistor's base leg and the resistor protected LED was soldered to the emitter? leg of the transistor. Two 15" lengths of what looks to be 24 ga. wire, terminated with alligator clips for the power supply finish it off. My advice is to be very careful with this DON'T short between any IC package pins. That will kill a chip dead. I'm sure it would be child's play for everyone here, except me and thee, to give the resistor values necessary (I can't see the all of the color bands on the probe resistor w/o taking the thing apart.) It won't tell if a pin or connection is 'pulsing' unless it is very, very slow but it will tell if a pin or connection has power. The brighter the LED the higher the voltage. Good luck.

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Re: Wireless Remote Control troubleshooting question

Post by Sparky Williams » Sun Feb 29, 2004 4:45 pm

Jwax<p>The circuit incorporates a linear regulator chip that provides 5 volts to power the circuit.

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Re: Wireless Remote Control troubleshooting question

Post by Sparky Williams » Sun Feb 29, 2004 4:49 pm

Edd,<p>How do I confirm that pins 3 and 8 are at the low position?

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Re: Wireless Remote Control troubleshooting question

Post by Sparky Williams » Sun Feb 29, 2004 4:51 pm

Edd,<p>Correction -- I meant pin 2, not pin 3.

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Edd
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Re: Wireless Remote Control troubleshooting question

Post by Edd » Sun Feb 29, 2004 9:30 pm

Using your metering in the DC mode:
Less than (decimal).4 Vdc= Logic low.
Greater than 2.5 VDC = Logic high,in the logic family that you are working with.
73's de Edd

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