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Is this motor driver controller IC capable of reading position info from potentiometer?

vestaviascott

Jul 28, 2013
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I'm specifically referencing two examples of H-bridge motor driver controller ICs (BD6210 and WT7901) to more fully understand and troubleshoot the circuitry of a typical exercise bike or elliptical's resistance/level controller. These consumer class exercise bikes and ellipticals all use the same basic setup for adjusting pedal load as described here:

The issue is that when the wall adapter's eventually wear out and start leaking out much higher voltage than the bikes are designed to operate at (most operate at 6-12 volts), this chip is typically the first to fail. I'm trying to determine if replacement of this chip should resolve this type of failure or if there may be other components involved in the resistance circuit, specifically to read the feedback of the DC motor's position sensor as described in the video above. Should these chips be capable of that as well as driving the motor?

BD6210
https://www.digikey.com/en/products/detail/rohm-semiconductor/bd6210f-e2/1936300

WT7901
http://www.weltrend.com/en-global/product/detail/66/86/273
 

Bluejets

Oct 5, 2014
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The issue is that when the wall adapter's eventually wear out and start leaking out much higher voltage than the bikes are designed to operate at

What free energy discussion did you obtain that information from...?
 

vestaviascott

Jul 28, 2013
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What free energy discussion did you obtain that information from...?
Are you serious right now?

Have you metered a used AC/DC wall adapter rated for 6 volts? It's pretty common over time for them to meter out at upwards of 3x rated output voltage. Apparently enough to fry these unprotected driver ICs commonly used in exercise bikes.

Troll much?
 
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Bluejets

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You cannot get accurate readings no load on any supply.
Any device with limited tolerence would have protection circuitry included.
 

WHONOES

May 20, 2017
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The measured voltage from a wall wart with an unregulated output can be substantially higher than its published value when measured off load, which I assume is what you have done.
 

vestaviascott

Jul 28, 2013
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The measured voltage from a wall wart with an unregulated output can be substantially higher than its published value when measured off load, which I assume is what you have done.
I buy 6, 9 and 12 volt DC Wall warts in bulk. When I receive them I meter them to insure they meter out at stated output voltage. I have yet to have one new that is not within .5 volts. Thats without load.
Over time, these same adapters gradually begin to meter out at 2-3x higher output voltage that stated.
 

vestaviascott

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Kinda off track from my central question, hopefully someone can address it?
 

kellys_eye

Jun 25, 2010
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components involved in the resistance circuit,
Not sure what you mean by that statement.

The two chips you reference have no capability to 'read position information'. In your example (the bike?) the position is fed back as a voltage (from a potentiometer physically connected to the motor output) and will be sensed by the controlling processor to determine the position. From that information the microprocessor will send a signal to the h-bridge IC to drive it in the appropriate direction.

The only additional input the IC has other than 'forward/backwards' is a pin that can be used to vary the speed of the motor using PWM (pulse width modulation).

As for:
eventually wear out and start leaking out much higher voltage
I have never seen or experienced this in 40+ years of electronics. Maybe physics has changed in that time though......
 

Tha fios agaibh

Aug 11, 2014
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Full disclosure i didn't watch video or know exactly what problems you have.

The Datasheet shows a H bridge driver which requires external PWM feedback before it can output power to the motor. I would see if your getting these pulses as well as power where needed before replacing it.
 

kellys_eye

Jun 25, 2010
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Have you metered a used AC/DC wall adapter rated for 6 volts? It's pretty common over time for them to meter out at upwards of 3x rated output voltage. Apparently enough to fry these unprotected driver ICs commonly used in exercise bikes.
No circuit that uses digital electronics will operate without using a stabilised (regulated) voltage source. If the immediate supply is via a wall wart then that voltage will be regulated by some onboard circuitry to keep it within the required logic levels used (5V, 3.3V, whatever). The onboard regulation should be capable of handling a wide input voltage swing without harming the circuitry.

No wall wart I've ever met has had even an offload voltage more than double it's nameplate rating (i.e. a 6V wart has NEVER read 12V never mind 3x that). The only way the output voltage can rise is if the input voltage rises - that's how transformers work.
 

Tha fios agaibh

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I'm guessing what VestavlaScott experienced was the regulator portion of an adapter may have failed causing higher than expected voltage especially when checked without a load.
 

vestaviascott

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I'm guessing what VestavlaScott experienced was the regulator portion of an adapter may have failed causing higher than expected voltage especially when checked without a load.
Thanks. Your answer sounds more in line with what I'm seeing. Basically a DC wall adapter measures more than its stated output voltage - I'm measuring it outside of load, simply plugged into the wall and metering with a MM at the barrel connector.

Perhaps an observed/measured output at the meter that is higher than stated/expected output is not enough to fry an IC chip, that's just my guess because I see so many of these bikes that have the same issues related to the resistance system while the other electronic circuitry (speed/rpm, pulse, user memory setup, etc) appears to work as expected. In almost every case, the adapter attached to the bike has a DC power adapter (most are 6 volts, some are 9 volts and a few are 12 volts) that meters out at higher than stated output voltage (physics be damned, lol).
 
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vestaviascott

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Full disclosure i didn't watch video or know exactly what problems you have.

The Datasheet shows a H bridge driver which requires external PWM feedback before it can output power to the motor. I would see if your getting these pulses as well as power where needed before replacing it.

The feedback originates from the user pressing an up button or a down button on the display console. "Up" signals to the microprocessor to increment the resistance level by one, down signals to decrease the resistance level by one.

The bikes usually have a range of resistance between 1-16 or 1-12, etc. The "resistance" relates to the amount of effort required to pedal the bike. Its regulated by a large bank of magnet's position/proximity in relation to the flywheel attached to the pedals.

The system uses a 6 volt stepper motor geared to a potentiometer to move the magnet back and forth in relation to the flywheel and report its position back to the console.
 
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vestaviascott

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No wall wart I've ever met has had even an offload voltage more than double it's nameplate rating (i.e. a 6V wart has NEVER read 12V never mind 3x that). The only way the output voltage can rise is if the input voltage rises - that's how transformers work.
Thanks again for your feedback. When I take a meter reading on these DC adapters, I put a piece of tape on them and with a black sharpie, I write the measured voltage on them. I went back to my collection of wall warts that I've tested and checked the stated vs measured voltage indications and its more in line with 1.5-2x, not 3x. I stand corrected.

So, from what you are saying, I don't have to worry much about any of these old 6 & 9 volt DC adapters causing damage to these exercise bike display consoles and circuits despite the higher than stated voltage?
 

kellys_eye

Jun 25, 2010
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I don't have to worry much about any of these old 6 & 9 volt DC adapters causing damage to these exercise bike display consoles and circuits despite the higher than stated voltage?
To a point.

As already mentioned, the output of those devices is UNREGULATED therefore tends to higher than the nameplate suggests (the nameplate refers to the voltage expected under the correct load).

If an unregulated power unuit is used then some other form of protection/regulation will ALWAYS be included - usually within the powered unit itself - but that doesn't mean it can take 'any' input. There will be a limit.

Assuming the LOADED voltage is close to the nameplate voltage then many devices with built-in regulation circuitry will be capable of working with up to 50% overload although this isn't recommended as there are limits to power dissipation by the regulating device and, the higher the voltage the more power is going to be dissipated in regulating it. Some equipment may even have input voltage limiting circuitry (and reverse polarity protection) as additional protection - not usually in cheap Chinese 'crap' though......

Unregulated wall warts serve their purpose though and they either work or don't - they don't 'change' output. If they are made correctly (again, cheap Chinese crap warnings apply) they will have an internal thermal fuse that blows if they are over-used rendering them useless (of course) otherwise, sans such protection, they are often the cause of house fires......
 

vestaviascott

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If an unregulated power unuit is used then some other form of protection/regulation will ALWAYS be included - usually within the powered unit itself - but that doesn't mean it can take 'any' input. There will be a limit.
Thanks for helping my understanding of how the DC adapters work. In my case, I'm obtaining used exercise bikes from various sources (thrift stores, fb marketplace, auctions, etc) and since the DC adapters are not permanently attached to the bikes, the chances of the OEM adapter being included with the bike is unknown and I don't assume it.

I haven't had any issues as long as the polarity and metered voltage of the DC adapter is a match to what the bike calls for. There is "usually" either a sticker or a stamped voltage and amp requirement near the power input socket (almost always 2 amps and either 6v or 9v and sometimes 12v for larger ellipticals.

I keep a stock of these 6 and 9 volt adapters on hand. And they have to be capable of min 2amp to work properly for these machines.

Without a voltage nameplate, I find that most Schwinn/Nautilus/Bowflex recumbent & upgright bikes use 9v-2a. Most NordicTrack/Proform makes call for 6v-2a. All center positive pin polarity.
 
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Tha fios agaibh

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Measuring the voltage unloaded doesn't prove the adapter is good.
For example you can measuring around 12v output of an adapter but that voltage can collapse to about 1v under a small load.

Better to use something like an old automotive light to load its output and then measure voltage.

You could use resistors as a load but they'll get too hot unless they have adequate wattage.
An old GE1156 lamp on the other hand I believe is rated for 10w. Plenty big to load most adapters.

Be careful about using the correct ratings. It's fine to have a larger supply current than you need, (for example 1amp adapter when you only require 500ma) but not less capacity than needed.
 

CircutScoper

Mar 29, 2022
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I keep a stock of these 6 and 9 volt adapters on hand. And they have to be capable of min 2amp to work properly for these machines.

An issue that I don't think has been mentioned (sorry if it has and I missed it) is that some adapters are internally regulated and will therefore produce an output that's within a few % of the number on the nameplate, while others are not and won't. The potential for disaster when mixing and matching unknown "generic" adapters with unknown loads should be obvious.
 

vestaviascott

Jul 28, 2013
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An issue that I don't think has been mentioned (sorry if it has and I missed it) is that some adapters are internally regulated and will therefore produce an output that's within a few % of the number on the nameplate, while others are not and won't. The potential for disaster when mixing and matching unknown "generic" adapters with unknown loads should be obvious.
When you say "unknown loads", would you consider the presence of a sticker or engraved marking next to the DC barrel plug socket like the one in the pic below in that category?

278578219_5153008208095329_3595313818370703892_n.jpg
 

kellys_eye

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That sticker would indicate (to me) that it required 9V with a minimum supply rate (capability) of 500mA.
 
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