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Electronic snap circuits (1 Viewer)

R

rascal

Footballguy
My parents got my six year old son an electronic snap circuit by elenco for Xmas (parents can't be here for actual xmas so we opened presents yesterday). First, this is a great gift as he is building the projects on his own which requires him to read and follow instructions...i heavily recommend it. Second, we are on project 5, of 300, and I'm already reaching the limits of my electrical knowledge.

Any electrical engineers in the house care explaining why the light dims when you take off the fan? Page 11 from the link below.

https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.elenco.com/admin_data/pdffiles/SC-100_REV-H1.pdf&ved=0ahUKEwi2seupjvHJAhXJKCYKHbm8DLwQFgh3MBA&usg=AFQjCNF0nCSqOgoaaSXxfuNo-KN5AcfWFQ

 
Last edited by a moderator:
rascal said:
My parents got my six year old son an electronic snap circuit by elenco for Xmas (parents can't be here for actual xmas so we opened presents yesterday). First, this is a great gift as he is building the projects on his own which requires him to read and follow instructions...i heavily recommend it. Second, we are on project 5, of 300, and I'm already reaching the limits of my electrical knowledge.

Any electrical engineers in the house care explaining why the light dims when you take off the fan? Page 11 from the link below.

http://www.elenco.com/admin_data/pdffiles/SC-100_REV-H1.pdf&ved=0ahUKEwj0n_v3gfHJAhVHRiYKHZoeD9oQFghwMBA&usg=AFQjCNF0nCSqOgoaaSXxfuNo-KN5AcfWFQ
Click to expand...
motor can spin faster without fan slowing it down, and draws more power dimming the light.

 
yeah these are neat gifts they are fun and they make kids smarter i salute your parents on this brohan tell them that they can take it to the bank for the ole swcer bromigo

 
gmbacm said:
rascal said:
My parents got my six year old son an electronic snap circuit by elenco for Xmas (parents can't be here for actual xmas so we opened presents yesterday). First, this is a great gift as he is building the projects on his own which requires him to read and follow instructions...i heavily recommend it. Second, we are on project 5, of 300, and I'm already reaching the limits of my electrical knowledge.

Any electrical engineers in the house care explaining why the light dims when you take off the fan? Page 11 from the link below.

http://www.elenco.com/admin_data/pdffiles/SC-100_REV-H1.pdf&ved=0ahUKEwj0n_v3gfHJAhVHRiYKHZoeD9oQFghwMBA&usg=AFQjCNF0nCSqOgoaaSXxfuNo-KN5AcfWFQ
Click to expand...
motor can spin faster without fan slowing it down, and draws more power dimming the light.
Click to expand...
I thought of that but the light is brighter at initial startup which seems contrary to inertia...takes more energy to speed it up than maintain, no? And with no governor on the motor shouldn't the power drawn be the same regardless of fan being on or not?

 
rascal said:
gmbacm said:
rascal said:
My parents got my six year old son an electronic snap circuit by elenco for Xmas (parents can't be here for actual xmas so we opened presents yesterday). First, this is a great gift as he is building the projects on his own which requires him to read and follow instructions...i heavily recommend it. Second, we are on project 5, of 300, and I'm already reaching the limits of my electrical knowledge.

Any electrical engineers in the house care explaining why the light dims when you take off the fan? Page 11 from the link below.

http://www.elenco.com/admin_data/pdffiles/SC-100_REV-H1.pdf&ved=0ahUKEwj0n_v3gfHJAhVHRiYKHZoeD9oQFghwMBA&usg=AFQjCNF0nCSqOgoaaSXxfuNo-KN5AcfWFQ
Click to expand...
motor can spin faster without fan slowing it down, and draws more power dimming the light.
Click to expand...
I thought of that but the light is brighter at initial startup which seems contrary to inertia...takes more energy to speed it up than maintain, no? And with no governor on the motor shouldn't the power drawn be the same regardless of fan being on or not?
Click to expand...
What a completely awesome gift! :)

I couldn't get your link to work, but it sounds like some sort of power limiting circuit may be involved, no? Just shooting in the dark (heh) since I can't see the link.

 
rascal said:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.elenco.com/admin_data/pdffiles/SC-100_REV-H1.pdf&ved=0ahUKEwi2seupjvHJAhXJKCYKHbm8DLwQFgh3MBA&usg=AFQjCNF0nCSqOgoaaSXxfuNo-KN5AcfWFQ

Try this link
Click to expand...
Ah, that works, thanks.

First of all, this is incalculably cool. How have I not heard of this company? Your parents rule.

So I think I'm supposed to be looking at Page 10, project #5. Looks like the light does not have an independent path to the power source, so when the fan is removed, that reduces the light's output? In project #6, by contrast, the light connects to the battery without going "through" the fan.

 
Aerial Assault said:
rascal said:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.elenco.com/admin_data/pdffiles/SC-100_REV-H1.pdf&ved=0ahUKEwi2seupjvHJAhXJKCYKHbm8DLwQFgh3MBA&usg=AFQjCNF0nCSqOgoaaSXxfuNo-KN5AcfWFQ

Try this link
Click to expand...
Ah, that works, thanks.

First of all, this is incalculably cool. How have I not heard of this company? Your parents rule.

So I think I'm supposed to be looking at Page 10, project #5. Looks like the light does not have an independent path to the power source, so when the fan is removed, that reduces the light's output? In project #6, by contrast, the light connects to the battery without going "through" the fan.
Click to expand...
Yes. Removing the fan dims the light. project 5 the fan/light are in series while in 6 they are parallel. So 5 is battery=fan+light, whereas six is battery = fan = lightIt's been 15 years since I had an electronics course. Wish I could find my textbook.

I'm sure it's because the motor draws more power with no fan, but it doesn't make sense in my head for reasons I previously stated

 
Last edited by a moderator:
rascal said:
Aerial Assault said:
rascal said:
https://www.google.com/url?sa=t&source=web&rct=j&url=http://www.elenco.com/admin_data/pdffiles/SC-100_REV-H1.pdf&ved=0ahUKEwi2seupjvHJAhXJKCYKHbm8DLwQFgh3MBA&usg=AFQjCNF0nCSqOgoaaSXxfuNo-KN5AcfWFQ

Try this link
Click to expand...
Ah, that works, thanks.

First of all, this is incalculably cool. How have I not heard of this company? Your parents rule.

So I think I'm supposed to be looking at Page 10, project #5. Looks like the light does not have an independent path to the power source, so when the fan is removed, that reduces the light's output? In project #6, by contrast, the light connects to the battery without going "through" the fan.
Click to expand...
Yeah, project 5 the fan/light are in series while in 6 they are parallel. So 5 is battery=fan+light, whereas six is battery = fan = lightIt's been 15 years since I had an electronics course. Wish I could find my textbook.
Click to expand...
Right. So the light dims when the fan is removed in 5 because part of the voltage goes to the fan's motor and part goes to the light, so you're seeing the effect of the overall power available being reduced. Are you asking why the light doesn't get brighter without the fan?

 
DC motors are strange little beasts. The power is the product of torque and angular speed. But, there is an inverse linear relationship between torque and angular speed for a given motor. The max power actually occurs when angular speed reaches 1/2 the no-load speed value (or when the torque is 1/2 the stall value, the amount that keeps the motor from turning). So, when the angular speed is maximized with no load on the motor, this is a lower power situation. Electrically, power = current X voltage. The low power condition with the fan blade off means less current flowing through the motor. Since it is in series with the bulb, the same amount of current must flow everywhere in the path, thus there is less current flowing through the bulb and it is dimmer.

 
My kids have this set. Great toy. One suggestion - I always have them remove one or both batteries from each holder. They build the circuits then I check for accuracy (shorts) before giving them the battery back. Prevents damage (worse?).

 
Galileo said:
DC motors are strange little beasts. The power is the product of torque and angular speed. But, there is an inverse linear relationship between torque and angular speed for a given motor. The max power actually occurs when angular speed reaches 1/2 the no-load speed value (or when the torque is 1/2 the stall value, the amount that keeps the motor from turning). So, when the angular speed is maximized with no load on the motor, this is a lower power situation. Electrically, power = current X voltage. The low power condition with the fan blade off means less current flowing through the motor. Since it is in series with the bulb, the same amount of current must flow everywhere in the path, thus there is less current flowing through the bulb and it is dimmer.
Click to expand...
Ah, never thought lower power was when the motor reached max speed. So basically the motor is acting as a variable resister.

Now how do I explain that to a six year old.. Lol

Thanks...I will probably bump this thread again

 
jabarony said:
My kids have this set. Great toy. One suggestion - I always have them remove one or both batteries from each holder. They build the circuits then I check for accuracy (shorts) before giving them the battery back. Prevents damage (worse?).
Click to expand...
Good idea

 
rascal said:
Galileo said:
DC motors are strange little beasts. The power is the product of torque and angular speed. But, there is an inverse linear relationship between torque and angular speed for a given motor. The max power actually occurs when angular speed reaches 1/2 the no-load speed value (or when the torque is 1/2 the stall value, the amount that keeps the motor from turning). So, when the angular speed is maximized with no load on the motor, this is a lower power situation. Electrically, power = current X voltage. The low power condition with the fan blade off means less current flowing through the motor. Since it is in series with the bulb, the same amount of current must flow everywhere in the path, thus there is less current flowing through the bulb and it is dimmer.
Click to expand...
Ah, never thought lower power was when the motor reached max speed. So basically the motor is acting as a variable resister.

Now how do I explain that to a six year old.. Lol

Thanks...I will probably bump this thread again
Click to expand...
Actually, the spinning motor, when current is flowing, generates an opposing EMF in the circuit. The true resistance of the motor's wires doesn't change, but in the end the effect is similar to having greater resistance.

ETA - here is a quick overview of the torque/power/speed relationship... http://lancet.mit.edu/motors/motors3.html This probably won't help with the 6 yr old, but you can get a sense of what is going on especially from the graphs in sections 3.1 and 3.2

 
Last edited by a moderator:
rascal said:
Galileo said:
DC motors are strange little beasts. The power is the product of torque and angular speed. But, there is an inverse linear relationship between torque and angular speed for a given motor. The max power actually occurs when angular speed reaches 1/2 the no-load speed value (or when the torque is 1/2 the stall value, the amount that keeps the motor from turning). So, when the angular speed is maximized with no load on the motor, this is a lower power situation. Electrically, power = current X voltage. The low power condition with the fan blade off means less current flowing through the motor. Since it is in series with the bulb, the same amount of current must flow everywhere in the path, thus there is less current flowing through the bulb and it is dimmer.
Click to expand...
Ah, never thought lower power was when the motor reached max speed. So basically the motor is acting as a variable resister.

Now how do I explain that to a six year old.. Lol

Thanks...I will probably bump this thread again
Click to expand...
I saw resistors covered a few projects down so if you want to explain it that way, tie it back in when he gets to those concepts. Basically, the fan being off, while in series with the light, is causing an interruption of the current and thus less power to the bulb.

 
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