Google Vibrator Switch & many types will be displayed including cutaways of my favorite, VIVS W-18010P.

 

If you can measure the resistance of the LDR when lit or dark, as well as measure the voltage (to ground) of both sides of the LDR when lit or dark (four measurements), it possible to use a switch to select between two resistors put in place of the LDR. This may require a SPDT push button switch. Share your results here.

Thanks. I haven’t

Here's a basic idea of how an LDR controlled circuit might work: (see image below)

Light changes the resistance which changes a voltage going to a comparator. Depending on the design the circuit does its thing. If you replace the LDR with the circuit (two resistors and a switch) pressing the button will change the voltage at the comparator the same as it does with the original LDR.

There are two ways of hooking up an LDR, one will drop the voltage the other will increase the voltage, depending on how it's wired. So my proposed change may or may not work. That's why more information is critical to finding a good solution to your problem.

View attachment 177022

Here's a basic idea of how an LDR controlled circuit might work: (see image below)

Light changes the resistance which changes a voltage going to a comparator. Depending on the design the circuit does its thing. If you replace the LDR with the circuit (two resistors and a switch) pressing the button will change the voltage at the comparator the same as it does with the original LDR.

There are two ways of hooking up an LDR, one will drop the voltage the other will increase the voltage, depending on how it's wired. So my proposed change may or may not work. That's why more information is critical to finding a good solution to your problem.

View attachment 177022

 

The problem is that the toy wasn’t working when I got it - so I don’t know how it works. The questions you asked were very good and things I hadn’t questioned - like how do you stop it running if it’s ONLY switch mechanism is light dependent? I will take a closer look at it after the weekend and then, hopefully, I MIGHT have something intelligent to add to the conversation.

As for taking out a good part and replacing it with another good part - I just figured it wouldn’t hurt to have some in my workshop as I hadn’t dealt with them before. And my reference books don’t mention LDRs at all so no help there.

I appreciate the patience of the people replying. I may be old but I am honestly not stupid (they don’t give PhDs to stupid people), I am just trying to learn a new skill without any training or support. The staff at my local electronics parts store unfortunately seem to know even less than I do.

 

Google Vibrator Switch & many types will be displayed including cutaways of my favorite, VIVS W-18010P.

Those are cool. I have some lights here that are activated by a little spring wiggling - in my “find out how that works some time” pile.
Vibration switches would be fantastic for a whole range of things with severely disabled children - not least of all as a seizure alert.
Thank you

 

Some questions I have that may be germane to the issue, how does the toy work? By that I mean if you block the LDR does the toy react for a set period of time controlled by the electronics within the toy? Or does it only react during the time the light has been blocked?

Also, if it's LDR, how do you stop the toy from running all night (or all day - depending on its operation)?

In the most general terms, as you already know, an LDR changes resistance with the exposure of light. It shouldn't be too hard to substitute the LDR with a switch and a couple resistors. The two resistors set up a voltage divider (don't worry if this is over your head, you'll catch on). The voltage divider will act like the LDR in the sense that it is now providing an unchanging and constant division in the voltage. Since the LDR requires a change in light levels to cause a change in the resistance, a switch in parallel with one of the two resistors can do the same thing in that when you push the button you change the voltage (same as the LDR will do) and activate the toy.

Before we start throwing schematics at you we need to understand a little more about the toys operation. That's why people are asking for more specific information. If you can manage to get that info to us I'm confident someone here will be able to come up with a brilliant and simple solution to the problem.

Good luck.

I have discovered this is the toy https://www.amazon.com/The-Roffle-Mates-Laughing-Alligator/dp/B002TMVYXO It is motion activated and the only other information I have is that where the LDR is in the PCB it reads V+ 330k V- 560k

 

I have discovered this is the toy https://www.amazon.com/The-Roffle-Mates-Laughing-Alligator/dp/B002TMVYXO It is motion activated and the only other information I have is that where the LDR is in the PCB it reads V+ 330k V- 560k

It's now plausible to think you are not dealing with an LDR but rather a PIR detector (Passive Infra Red). If the toy is motion activated then you don't need a switch. This should be even easier to use by a child who's mental capabilities are not on par with contemporary children.

If it IS a PIR detector then fixing it will be a little more involved than simply replacing it with a switch. I'm sure a switch could be bodged into the circuit, but now the child has to touch something, whereas previously all they had to do was come within its field of detection. I'm not the one to assist you with PIR; so I think I'm probably done with responding to this post as I don't think I can add anything useful to you.

 

It's now plausible to think you are not dealing with an LDR but rather a PIR detector (Passive Infra Red). If the toy is motion activated then you don't need a switch. This should be even easier to use by a child who's mental capabilities are not on par with contemporary children.

If it IS a PIR detector then fixing it will be a little more involved than simply replacing it with a switch. I'm sure a switch could be bodged into the circuit, but now the child has to touch something, whereas previously all they had to do was come within its field of detection. I'm not the one to assist you with PIR; so I think I'm probably done with responding to this post as I don't think I can add anything useful to you.

Here is a photo of it. I have PIRs and they look different. And the children can’t make purposeful movements to activate something that requires motion as they are quadriplegic. Some have switches they activate with their heads because it’s the only part of the body they have control over and even then only with neck bracing to support the head. They also frequently have CVI which is cortical vision impairment meaning their eyes are fine but the brain doesn’t interpret. So they can’t locate the area that requires motion, even if they could do it. That’s way I struggle because they need have to be toys that move so the child can hear the movement, and sound. And lights though I haven’t gotten to adding lights into the equation yet.

But thanks for your time, much appreciated

 

It's now plausible to think you are not dealing with an LDR but rather a PIR detector (Passive Infra Red). If the toy is motion activated then you don't need a switch. This should be even easier to use by a child who's mental capabilities are not on par with contemporary children.

If it IS a PIR detector then fixing it will be a little more involved than simply replacing it with a switch. I'm sure a switch could be bodged into the circuit, but now the child has to touch something, whereas previously all they had to do was come within its field of detection. I'm not the one to assist you with PIR; so I think I'm probably done with responding to this post as I don't think I can add anything useful to you.

And apologies, I am dealing with children with physical disabilities (primarily cerebral palsy) and they frequently don’t have intellectual disabilities although people often assume they do because they can’t do anything without assistance and are frequently non-verbal

 

https://www.adafruit.com/product/16...ds2aYU3D8jWYPpeYqLlvSneU0_ojKZLRoCOqgQAvD_BwE

 

@Sstanier I chose this terminology

This should be even easier to use by a child who's mental capabilities are not on par with contemporary children.

in an effort to not be insensitive to those with disabilities. Please excuse my lack of understanding in such manor. I've not been placed in any circumstances to ever have to deal with such a handicap.

 

Personally I find it challenging sometimes to try to understand what people want or are asking for. Sometimes the requested solution seem at odds with what I picture. I have the same issues when I’ve posted. Not enough information, not specific enough... so on.

For your project it would seem to me that a nod of the head would be easier to activate rather than something you would have to push with your nose or chin. I’m sure I’m wrong but being a sensitive subject I am hesitant to ask.

The photoresistor that you showed works by detecting difference in light. It’s not certain to me how it works in your device. Perhaps it’s just the change that’s detected. Again could be a number of ways this is used. Whether a switch can be replaced is not certain without understanding the circuit. With the device removed I wonder if it’s safe to short the junction. Maybe it works inversely and detects dark which might mean a person is nearby. Maybe you need a NC switch that opens on push. Maybe it’s the other way. Perhaps you can experiment. You may need a resistor added to replace the resistance on the photoresistor. Maybe you can measure the resistance in full light and add that with your switch to ensure you’re not changing the circuit and perhaps over voltage/over current situation.

Might work

 

Hello,

The site that @Wolframore showed you has also a tutorial about the photocell:
https://learn.adafruit.com/photocells

Bertus

 

I think that The PIR can be paralleled or replaced with an appropriate external switch if enough information can be gleaned.
Where are you located?

 

I think that The PIR can be paralleled or replaced with an appropriate external switch if enough information can be gleaned.
Where are you located?

See post #27. Photo shows LDR and not PIR.

 

Roffle is " Motion Activated". " and when he passed it " Gator" started laughing", so as I had suspected the shiney round thing in the shell top
might be a speaker, post # 12 picture. I still have no clue as to where the LDR fits in.
Might there be different Roffle models ?
Pressure switches can be made from Velostat, a pressure sensitive plastic sheeting of
which I have some samples also some samples of tilt switches & vibrator switches.

 

I think that The PIR can be paralleled or replaced with an appropriate external switch if enough information can be gleaned.
Where are you located?

I am in Perth, Western Australia. I am waiting on some replacement equipment I need - once it arrives I will start experimenting with the toy. It’s seems there is a fault that is not related to the LDR which I currently can’t find. He definitely works because I can get him to operate by bypassing the circuit entirely and just providing an external power source directly to the motor. Finding faults in PCBs, for me, is just dumb luck - there is just so much I don’t know! I know components and what they all do, it’s the circuitry that baffles me because I don’t have a schematic and I guess you can “read” the board but that’s not a skill set I have

 

Roffle is " Motion Activated". " and when he passed it " Gator" started laughing", so as I had suspected the shiney round thing in the shell top
might be a speaker, post # 12 picture. I still have no clue as to where the LDR fits in.
Might there be different Roffle models ?
Pressure switches can be made from Velostat, a pressure sensitive plastic sheeting of
which I have some samples also some samples of tilt switches & vibrator switches.

I am not sure what you are asking. The “motion sensor” was a small black spout between his eyes and in my photograph it’s the two brown wires at the front of the board, next to the screw in front of the motor.

It seems I have some tilt switches - they are in my “I don’t know what these components are yet” collection. Any toys that are not suitable for these particular children I harvest parts from rather than just discard them.

 

Roffle is " Motion Activated". " and when he passed it " Gator" started laughing", so as I had suspected the shiney round thing in the shell top
might be a speaker, post # 12 picture. I still have no clue as to where the LDR fits in.
Might there be different Roffle models ?
Pressure switches can be made from Velostat, a pressure sensitive plastic sheeting of
which I have some samples also some samples of tilt switches & vibrator switches.

These are the switches that cause the most problems - they couldn’t be simpler but for some reason they consistently don’t fulfil their purpose. I also have switches operated by magnet - useless in my toys but I now have a collection of incredibly strong magnets that may be useful sone day

 

I worst comes to worst just eliminate the circuit board and just switch the two motors using a driver if desired. The switch should match the needs of the child user.