Hovercraft B/C

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antoine_ego
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Re: Hovercraft B/C

Post by antoine_ego » February 6th, 2017, 11:49 am

NyeSpy wrote:Does anyone know if a rotary dimmer would work to vary the speed of the push fan? We will be using two 7.2v NiCd RC racing batteries, one for the lift fan and one for the push fan.

Push fan - http://www.digikey.com/product-detail/e ... ND/5209819
Rotary dimmer in question - https://www.lowes.com/pd/Lutron-Rotary- ... er/1059607

Thoughts?
Since rotary dimmers are basically variable resistors, assuming you can connect them, you should be able to use them. Since you are running 7.2V batteries, and these dimmers are meant for maximum 120V, I would think they would work.
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Re: Hovercraft B/C

Post by 0ddrenaline » February 6th, 2017, 2:21 pm

NyeSpy wrote:Does anyone know if a rotary dimmer would work to vary the speed of the push fan? We will be using two 7.2v NiCd RC racing batteries, one for the lift fan and one for the push fan.

Push fan - http://www.digikey.com/product-detail/e ... ND/5209819
Rotary dimmer in question - https://www.lowes.com/pd/Lutron-Rotary- ... er/1059607

Thoughts?
I believe that we considered a dimmer but it had an integrated circuit. I think the dimmer in that link will work if it doesn't have an integrated circuit.

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Re: Hovercraft B/C

Post by andrewwski » February 6th, 2017, 10:14 pm

antoine_ego wrote:
NyeSpy wrote:Does anyone know if a rotary dimmer would work to vary the speed of the push fan? We will be using two 7.2v NiCd RC racing batteries, one for the lift fan and one for the push fan.

Push fan - http://www.digikey.com/product-detail/e ... ND/5209819
Rotary dimmer in question - https://www.lowes.com/pd/Lutron-Rotary- ... er/1059607

Thoughts?
Since rotary dimmers are basically variable resistors, assuming you can connect them, you should be able to use them. Since you are running 7.2V batteries, and these dimmers are meant for maximum 120V, I would think they would work.
Dimmers are typically *not* variable resistors (rheostats/potentiometers). If they were, they'd have to dissipate a LOT of heat when the light was dimmed, and would get very hot.

Dimmer switches are used in AC, and they essentially "chop" the sine wave. When the polarity switches direction (crosses zero), it cuts the power supply until the wave reaches a certain voltage, at which point it allows it back through. This voltage is what you're controlling through the dimmer.

Most dimmers contain integrated circuits, which are not allowed in this event. But they won't work on DC anyway.

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Re: Hovercraft B/C

Post by keastman » February 7th, 2017, 8:02 am

In regards to "vehicles must have an electric switch to permit safe starting"... If you are using two motors can they each be turned on with a separate switch or do they have to be linked to a single switch to turn it on?

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Re: Hovercraft B/C

Post by HandsFreeCookieDunk » February 7th, 2017, 9:02 am

keastman wrote:In regards to "vehicles must have an electric switch to permit safe starting"... If you are using two motors can they each be turned on with a separate switch or do they have to be linked to a single switch to turn it on?
Disclaimer: This is one man's opinion and is in no way an official rules clarification.

I can't imagine that would be a problem. As long as you are safely starting all your fans, I don't see why a supervisor would care what order you do it in.

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Re: Hovercraft B/C

Post by kenniky » February 7th, 2017, 9:22 am

keastman wrote:In regards to "vehicles must have an electric switch to permit safe starting"... If you are using two motors can they each be turned on with a separate switch or do they have to be linked to a single switch to turn it on?
Ours had multiple switches. It should be fine.
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Re: Hovercraft B/C

Post by NyeSpy » February 7th, 2017, 12:05 pm

I have had multiple electronics "gurus" suggest using a discrete transistor circuit to control the push fan speed. I am being told that this would not be the same as an integrated circuit. Before I invest a ton of time learning about discrete transistor circuits, are they allowed for this event?

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Re: Hovercraft B/C

Post by chalker » February 7th, 2017, 3:40 pm

NyeSpy wrote:I have had multiple electronics "gurus" suggest using a discrete transistor circuit to control the push fan speed. I am being told that this would not be the same as an integrated circuit. Before I invest a ton of time learning about discrete transistor circuits, are they allowed for this event?
As usual, this is not the place for official statements. SOINC is where you should go for that. Unofficially though:

We’ve had this situation come up in previous years / other events as well. Technically this is correct, in that a single transistor does NOT meet the definition of an integrated circuit. Last year I personally saw an amazing Mission Possible device where the kid had essentially constructed an ASIC out of LOTS of individual transistors to get around the no ICs rule. The issue is that while I closely inspected it, I didn’t have the time, nor the ability wihout deconstructing it to verify each and every component was only a transistor and he hadn’t snuck a true IC into it.

Hence, I would point out that most event supervisors won’t have the knowledge / ability to verify that a given small black box is a single transistor vs. an integrated circuit (for example, some voltage regulators look EXACTLY like a transistor but clearly are an IC). You will be at risk to having your device DQ’d if you bring something with lots of transistors that can’t be verified in a timely manner by an unskilled supervisor.

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Re: Hovercraft B/C

Post by RJohnson » February 8th, 2017, 2:45 pm

chalker wrote:
NyeSpy wrote:I have had multiple electronics "gurus" suggest using a discrete transistor circuit to control the push fan speed. I am being told that this would not be the same as an integrated circuit. Before I invest a ton of time learning about discrete transistor circuits, are they allowed for this event?
As usual, this is not the place for official statements. SOINC is where you should go for that. Unofficially though:

We’ve had this situation come up in previous years / other events as well. Technically this is correct, in that a single transistor does NOT meet the definition of an integrated circuit. Last year I personally saw an amazing Mission Possible device where the kid had essentially constructed an ASIC out of LOTS of individual transistors to get around the no ICs rule. The issue is that while I closely inspected it, I didn’t have the time, nor the ability wihout deconstructing it to verify each and every component was only a transistor and he hadn’t snuck a true IC into it.

Hence, I would point out that most event supervisors won’t have the knowledge / ability to verify that a given small black box is a single transistor vs. an integrated circuit (for example, some voltage regulators look EXACTLY like a transistor but clearly are an IC). You will be at risk to having your device DQ’d if you bring something with lots of transistors that can’t be verified in a timely manner by an unskilled supervisor.
I've used discrete transistors in no IC events before, and I've had two types of ES's: 1. Those that just take my word for it. 2. Those who are cool with it after I show them the technical specifications. Buy a product with a number on it so the specs sheet matches and that verifies it for them.

Good luck!

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Re: Hovercraft B/C

Post by windu34 » February 9th, 2017, 8:01 am

NyeSpy wrote:I have had multiple electronics "gurus" suggest using a discrete transistor circuit to control the push fan speed. I am being told that this would not be the same as an integrated circuit. Before I invest a ton of time learning about discrete transistor circuits, are they allowed for this event?
What is the advantage of using a switching circuit made up of transistors to control speed over regulating current to the motor with a variable resistor?
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