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Bloogoo

Why won't it work?

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I don't know where to post this, and I don't know where to find information about it on the internet. I'm stuck (and trust me, I've searched). Hopefully someone will be able to help me :D

I have a remote control boat that doesn't work. Power (as measured with a multimeter) is flowing through the circuit board *everywhere* except to the engines. The connection to the engines come from two transistors, something similar to this:

x-x-x <== Transistor

--o-- <== Connection to engine

x-x-x <== Transistor

Now I'm not 100% fluent in electronics (I'm teaching myself at the moment). I don't know much about transistors, and I'm not sure how to test if they're still working, but I've found this page that helps: http://www.kpsec.freeuk.com/components/tran.htm. I've followed the instructions for testing a transistor, and according to the instructions given, all transistors are working.

What do I do now? I'm completely stuck, and would love to get this boat up and running. I don't know if it's an issue with a transistor. I don't know if it's an issue with another component. All I know is that the boat doesn't work, and the engines don't spin. What can I do?

I don't know what other information is needed to help me, but if anyone could lend a hand I would be *very* grateful!

Thanks in advance.

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Info on the boat would be helpful. Type motor, motor size, speed control name, type & current rating, batteries being used, Rx name & type, any technical specs you can find would be nice. Have you tried the mfgrs website for info??

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Why not try the local Model Boat Club if there is one? They usually have an "expert" who could help - also a lot of Boat clubs have web pages/forums where your question would be more than likely be answered quickly... just Google

Model Boat Club..dozens there.

Edited by rossmans

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Info on the boat would be helpful. Type motor, motor size, speed control name, type & current rating, batteries being used, Rx name & type, any technical specs you can find would be nice. Have you tried the mfgrs website for info??

The boat is just a cheap, generic model boat without any distinguishing markings on it. The decals say "speed ocean", "master", and "endless power" but those are the only labels on it. I'm not sure about the motors - they too don't have any distinguishing markings, and I don't know how to test them/what to test them for. I'm running it off of a homemade 7.5V battery pack because the 7.2V battery pack that it came with was dead and couldn't (as far as I know) be recharged. I also don't know the manufacturer - it was a gift from about 5 years ago that stopped working last summer.

Why not try the local Model Boat Club if there is one? They usually have an "expert" who could help - also a lot of Boat clubs have web pages/forums where your question would be more than likely be answered quickly... just Google

Model Boat Club..dozens there.

I will search for one in my area. Thanks for the suggestion.

Are the transmitter and receiver even working at all?

I hope so :D but I'm not sure how to test this.

Maybe post some close up pictures.

I'll try to post some within the next 48 hrs.

Edited by Bloogoo

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Ok, now I have some pictures. Hopefully I can explain myself a little clearer. Pictures are posted here: http://s4.photobucket.com/albums/y113/bloogoo/Boat/

Boat_01.jpg - This is my boat. As you can see it's just a cheap little RC boat that really has no monetary value, and unless I can get it to work (relatively) well, it will probably be thrown out.

Boat_02.jpg - One of two DC motors.

Boat_03.jpg - This is a quick little circuit I put together this morning to make sure that both motors were working. It's powered by a 7.5V source (homemade battery pack), and has (I think) a 12 ohm resistor in it. Ignore the green areas in the picture, as they were just extra pieces that were laying on the workbench and I didn't want them to be lost. The motors were wired in parallel and seemed to work fine.

Boat_04.jpg & Boat_05.jpg - The original transmitter portion of the RC boat. I'm not sure if this transmits or not, and I don't know how to find that out. All I know is that the red LED works when you push one of the switches.

Boat_06 & Boat_07.jpg - The original receiver portion of the RC boat. This is in the boat (duh!) and I'm not sure if it receives (see above).

I'm willing to take apart and rebuild the transmitter/receiver circuits, and I don't mind putting in the parts/money to do so, but I'd love to be able to reuse as much as possible. I've also found this PDF file which describes the transmitter/receiver chips, so I'm going to have a look at that and see what I can decipher. Any further help would be appreciated.

Edited by Bloogoo

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If you have a multimeter then you can check the output from the IC pins as in your PDF, that would make a good start.

Terry

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I'd be willing to bet my last .02 that the Tx and RX diagrams as shown in the PDF are used in the boat and and a typical boat like this would probably cost $30 to $40 (which is not a detriment as it provides lots of fun for the money). You can also measure the TX antenna connection and pin 9 on the board to see if there's any increased voltage indication when you push a button.

It may help to use a small signal diode on the meter probe as a demodulator on the Tx antenna output point on the board. If you measure a small increase in voltage when the buttons are pushed, in all likelihood the TX is working.

Do the same on the output pins of the Rx IC that correspond to the button you push on the TX... It appears that the voltages on the Rx IC output pins would be a logical 1 or 0 with 1 being an increased voltage reading.

The outputs could also be a pulse train, but in any event you would measure a voltage when the TX button is pushed that corresponds to that pin out. All of the above will tell you whether the TX and RX are working.

It appears that one motor is only used for directional control and only operates when turning left or right. The propulsion motor operates at two speeds forward and one reverse. None of them proportional. A scope sure would be handy if you could get your hands on one for an hour or two.

If you have an FM radio, there's the chance that you may be able to get an indication that the Tx is working by listening to see if you can hear any indication on the 4th harmonic of the TX around 108 mhz when pulsing the buttons.

Maybe Terry has a better idea for measuring pulsed outputs. My mind is a bit rusty on this without a scope and the equipment in hand.

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If you have a multimeter then you can check the output from the IC pins as in your PDF, that would make a good start.

Stupid question #1: How do I do that? I've taken my first reading from Vdd on the TX-2B chip connected (+) to Vdd and (-) to GND, and I get a reading of 0.40V. It says on p.3 of the PDF that the operating voltage is 1.5V min and 5.0V max. I'm nowhere near this. I've also tried pressing the buttons to see if the voltage will go up, but I still get the 0.40V.

What is the proper procedure for determining the output from IC pins? As I type this, I realize that I should probably do a Google search to find the results. That's where I'm off to now :)

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Use the multimeter to check the voltage at pins 3 & 9 of the TX with a good battery and it switched on, what do you get ?

Do the same for pins 2 & 13 on the RX, what do you get ?

Terry

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It appears that one motor is only used for directional control and only operates when turning left or right. The propulsion motor operates at two speeds forward and one reverse. None of them proportional. A scope sure would be handy if you could get your hands on one for an hour or two.

Is that the only way that the boat will run? Is there a way that both engines could be set up to control direction and speed, or would that involve major changes?

Use the multimeter to check the voltage at pins 3 & 9 of the TX with a good battery and it switched on, what do you get ?

Do the same for pins 2 & 13 on the RX, what do you get ?

Do the same on the output pins of the Rx IC that correspond to the button you push on the TX... It appears that the voltages on the Rx IC output pins would be a logical 1 or 0 with 1 being an increased voltage reading.

Thanks for pointing me in the right direction :D I'll list off the pins and their readings with respect to the GND (pin 3), both before a button (or the corresponding direction) is pushed, and after, as well as what they correspond to according to the PDF [i.e. pin / voltage with no button pushed (V) / voltage with button pushed (V) / configuration]

**********************

TX-2B

=====

1 0.20 0.59 Right

2 0.00 1.04 Test

3 --- --- GND

4 0.20 1.03 Backward

5 0.20 1.03 Forward

6 0.01 0.77 Turbo

7 0.00 0.33 SC

8 0.00 0.65 SO

9 0.20 0.40 VDD

10 0.00 0.40 PC

11 0.00 0.09 OSCO

12 0.00 0.65 OSCI

13 0.00 0.57 FOSC

14 0.20 1.00 Left

Battery 9.00

RX-2B

=====

1 2.36 2.29 VO2

2 --- --- GND

3 2.35 2.29 SI

4 2.05 2.05 OSCI

5 2.13 2.13 OSCO

6 0.00 0.00 Right

7 0.00 0.00 Left

8 3.96 3.96 ROB

9 0.82 0.82 VI2

10 2.39 2.38 V01

11 0.81 0.81 VI1

12 4.07 4.07 VDD

13 0.00 0.00 TURBO

14 0.00 0.00 FORWARD

15 0.00 0.00 BACKWARD

16 3.96 3.96 LDB

Battery 7.73

**********************

As far as I can tell, it seems that the RX-2B is the culprit, and that the signal that would send power to the controls (forward, backward, left, right, turbo) does not do what it's supposed to, and *that's* why it doesn't move. Am I correct? How can I fix this? Also, should the other values for the RX-2B change when buttons are pushed? If so, by how much?

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Pin 13 you have as TURBO but it is not, it is battery volts and you say it has 0v.

Pins 6,7,10,11,12 should go high as the correct button is pressed on the TX.

Terry

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Pin 13 you have as TURBO but it is not, it is battery volts and you say it has 0v.

Pins 6,7,10,11,12 should go high as the correct button is pressed on the TX.

Terry

I think I might have just confused the labeling on pin 13 - I'll double check it tomorrow. As for the other pins (including 13) they did not change when any of the buttons were pressed on the TX. I'm going to double check the antenna connection to the RX as well ... I removed the antenna so that I could more easily work with the circuit board, and may not have correctly soldered it back on. Should the antenna wire be connected to a capacitor, as seen in this photo? The antenna is connected at the bottom right (where it says "AN") and if it's not connected to the capacitor directly beside the "AN" then it's not connected to anything at all. I'm going to recheck my solder point (I know I should have done that in the first place :huh: ), and post the results. Hopefully I'll have better luck.

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Connect it to the cap....

Connected it to the capacitor.

Pin 13 you have as TURBO but it is not, it is battery volts and you say it has 0v.

Pins 6,7,10,11,12 should go high as the correct button is pressed on the TX.

I only confused the labels on Turbo and VDD (they should be switched). The values don't really change, even with the antenna connected to the capacitor :(

Edited by Bloogoo

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I think I'm just going to give up on getting this to work as an RC vehicle, and instead hook the motors up to a simple on/off switch so the boat will run in the water. I don't imagine *that* will be too hard, as (I think) it's just a simple connection from the batteries to the motors. I've made the motors go while it's connected to a breadboard, so I think I might connect them to a blank circuit board and go from there ... unless there are other suggestions :P

I want to thank everyone for their time and their efforts to help me further myself. I really appreciate it! :D

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You could look around on eBay for a cheap 27mc set, chop the motors off & patch the hull, add a rudder & servo and just sail it around. Add a bit more line on the mainsail though so it will travel out about 30 degrees from the hull C/L ...

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As I said you have no power going in to your RX chip :o

Try putting that right before you give up ;)

Terry

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As I said you have no power going in to your RX chip :o

Try putting that right before you give up ;)

I haven't given up yet :D I've checked the values of all the RX pins (again) after getting a more stable power connection, and these are the values that I found when tested against GND:

PIN SYMBOL VALUE (V) DESCRIPTION

==================================

1 VO2 2.38 Inverter2 output pin for power amplify

2 GND 0 Negative power supply

3 SI 2.37 Input pin of the encoding signal

4 OSCI 2.07 Oscillator input pin

5 OSCO 2.15 Oscillator output pin

6 RIGHT 0 Rightward output pin

7 LEFT 0 Leftward output pin

8 RDB 4.03 Rightward function disable, if this pin is connected to GND

9 LDB 4.04 Leftward function disable, if this pin is connected to GND

10 BACKWARD 0 Backward output pin

11 FORWARD 0 Forward output pin

12 TURBO 0 TURBO output pin

13 VDD 4.14 Positive power supply

14 VI1 0.83 Inverter1 input pin for power amplify

15 VO1 2.44 Inverter1 output pin for power amplify

16 VI2 0.83 Inverter2 input pin for power amplify

Now I have a few questions, hopefully someone can help me.

1.) There is power to the RX as VDD is 4.14V when tested to GND

2.) Should RDB and LDB have values greater than 0 when tested to GND? If so, does that not disable left and right?

3.) The SI value doesn't change, even when I push buttons on the TX. Does that mean that it's not getting *any* signal, or just a signal at it's specific frequency?

4.) Should this RX circuit be connected like the one given in the PDF that I found? I've attached it to this post. If it's not set up like that, should it be? Or has the manufacturer changed it around to work a different way?

5.) If it should be set up like that, should I make it like that? (ie should I rebuild the circuit)?

Receiver.pdf

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1. Good

2. Both should actuate their respective control when not grounded. Grounded is disabled or no signal.

3. The SI signal probably should not change as it should be a pulse train input. Need an Oscope to prove it.

4. I should imagine it should as probably very little engineering time was put into the equipment.

5. What in particular is different between your unit and the PDF?

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5 is the big question, we are assuming you have the circuit in the PDF. It would be good to spend a bit of time with a pen and paper checking it. If you don't have any voltage change on pins 6,7,10,11, 12 when you push the buttons then take a look at the TX. Start with checking the chip gets the correct volts going in then check for RF out the aerial. Do you have a radio that can pick up 27Mhz ?

Terry

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