Mounting of duet wifi and duex5
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Hi there,
On the documentation I found the following information about the mounting of the duet wifi and the duex expansion
"The Duex5/2 is designed to be mounted back-to-back with the Duet WiFi using long M4 screws and spacers"
What does that mean BACK to BACK ?
Anyone have a photograph which shows what that means ?
Kind regards,
Bart
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There is one here:
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Hi Bart,
You can also mount the Duet and Duex one above the other but on the same plane. Here is a link to an enclosure that I designed for this purpose http://www.thingiverse.com/thing:1859048. but there are other designs on thingiverse. The main thing to watch out for is that the power link (Vin) between the boards has to kept as short as possible.
Although the Wiki indicates that the boards should be mounted back to back, if you are likely to be pushing the stepper current up to 2.4 Amps (or even if not), then it will be advisable to blow cooling air onto the back of the boards. This might be difficult to do with them mounted back to back which is why I designed my enclosure the way I did, as it allows cooling fans to blow onto the back of each board.
HTH
Ian -
You can also mount the Duet and Duex one above the other but on the same plane. Here is a link to an enclosure that I designed for this purpose http://www.thingiverse.com/thing:1859048. but there are other designs on thingiverse. The main thing to watch out for is that the power link (Vin) between the boards has to kept as short as possible.
Just to be clear, it's the ground (negative) wire between the two VIN terminal blocks that needs to be short and thick. The positive one doesn't matter, you can have separate positive wires from each terminal block back to the power supply if you wish.
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Ah OK. Thanks.
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Just to be clear, it's the ground (negative) wire between the two VIN terminal blocks that needs to be short and thick.
Could you explain, please, why that is so?
Thanks.
Frederick
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Just to be clear, it's the ground (negative) wire between the two VIN terminal blocks that needs to be short and thick.
Could you explain, please, why that is so?
Thanks.
Frederick
The following is a copy and paste from the wiki instructions for wiring the expansion boards:
Important! You must have a reliable low-resistance connection between the negative (ground) terminals of the two VIN terminal blocks. Failure to do so may result in high currents flowing in the ground connectors of the ribbon cable and may cause damage to the Duet WiFi or Duex5. Preferably, make this connection using either solid core wire, or stranded core wire with ferrules of the correct size crimped on securely. Re-tighten the terminal block screws regularly for the first few days of use, to make sure there is no creep in the wires causing the screws to become loose.
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The heaters and especially the stepper drivers switch large currents on and off very quickly. Although the capacitors on the Duet and the DueX smooth out the currents a lot, this switching still creates noise on the power supply wires unless they are very short, because of the inductance and resistance of the wires. Noise on the +ve power input doesn't matter much. However, the negative input is connected to signal ground, and all the signals carries by the expansion bus are relative to ground, apart from the thermistor inputs which have their own analog ground.
Therefore, if you don't have a short thick ground wire between the VIN terminal blocks of the Duet and DueX but instead each one has a long ground wire back to the power supply terminal, then the Duet and the Duex can have grounds at slightly different potentials, and two bad things can happen:
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The signals sent between the Duet and the DueX may get corrupted
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Large currents may flow in the ground conductors of the ribbon cable, and if these currents are large enough then the ribbon cable conductors or connectors could burn out.
My recommendation is to use a twin-entry ferrule for the ground side of the VIN terminal block on the Duet. From it, one wire goes to the power supply, and the second one goes to the DueX. This second wire should be kept short.
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My recommendation is to use a twin-entry ferrule for the ground side of the VIN terminal block on the Duet. From it, one wire goes to the power supply, and the second one goes to the DueX. This second wire should be kept short.
Thank you.
Frederick
