Vr3 + HUD connected to 1 cell !!!!

Pierre Farrugia · 27th November 2005, 19:17

Hello,

Can someone explaine to me if I can connect 2 devices, eg a VR3 and a HUD circuit to one cell ? Has anyone tried this out ? Also in URI HUD he connected everything to the YBOD cells, can someone explaine to me how this can be done (not how to connect wires i.e. imparallel) but if additional resistors or circuits are nesessary not to effect the YBOD ? EG a VR3 works with one cell, the HUD I build works on 1 cell, can I just connect both to one cell ? My circuit uses the famous 10K across the sens and uses an opamp as a buffer as well!

Mark Chase · 27th November 2005, 20:30

My Uri HUD is conected to all three cells using a loomb that just goes in series with the existing loom. Un plug ends from molex conectors plug into HUD blug HUD ends back into Molex. VR3 is linked into cell one through the HUD control box.

Non crimping conectors are used.

Resistors are used to buffer the circuit but I cant tell you how its done. Sufice as to say a total short o the HUD does not afect the readings on the hand sets.

ATB

Mark Chase

Scuba_Vixen · 28th November 2005, 01:23

Quote: (Originally Posted by Pierre Farrugia)

Hello,

Can someone explaine to me if I can connect 2 devices, eg a VR3 and a HUD circuit to one cell ? Has anyone tried this out ? Also in URI HUD he connected everything to the YBOD cells, can someone explaine to me how this can be done (not how to connect wires i.e. imparallel) but if additional resistors or circuits are nesessary not to effect the YBOD ? EG a VR3 works with one cell, the HUD I build works on 1 cell, can I just connect both to one cell ? My circuit uses the famous 10K across the sens and uses an opamp as a buffer as well!

Since a VR3 is intended to be a "stand alone" load on a cell, it has a 10K ohm resistor accross the cell leads built in.

The 10K ohm resistor is there to balance the temperature compensation network of the cell.

If you connect 2 loads, each with a 10K resistor, the net effective resistance is then 5K ohms.

That would introduce some inaccuracy in the cells output. The degree of inaccuracy would vary with temperature and PO2.

If you don't use a 10K resistor accross the input of the op amp in the HUD circuit, ... Then....

Since the VR3 already has the 10K resistor, if you just connect the HUD in parallel with it, the cell won't see anything different than with just the VR3 ...

If you should want to use the HUD, but not the VR3, then you'd need to put the 10k resistor back in it.

It would be nice to see a schematic of the input stage of your HUD, but as long as you have an op amp as the load on the cell, it should have a decently high impedance.

Just leave the 10K resistor out of the HUD circuit and put it and the VR3 in parallel.

Darlene

Pierre Farrugia · 28th November 2005, 13:04

Quote: (Originally Posted by Scuba_Vixen)

Since a VR3 is intended to be a "stand alone" load on a cell, it has a 10K ohm resistor accross the cell leads built in.

The 10K ohm resistor is there to balance the temperature compensation network of the cell.

If you connect 2 loads, each with a 10K resistor, the net effective resistance is then 5K ohms.

That would introduce some inaccuracy in the cells output. The degree of inaccuracy would vary with temperature and PO2.

If you don't use a 10K resistor accross the input of the op amp in the HUD circuit, ... Then....

Since the VR3 already has the 10K resistor, if you just connect the HUD in parallel with it, the cell won't see anything different than with just the VR3 ...

If you should want to use the HUD, but not the VR3, then you'd need to put the 10k resistor back in it.

It would be nice to see a schematic of the input stage of your HUD, but as long as you have an op amp as the load on the cell, it should have a decently high impedance.

Just leave the 10K resistor out of the HUD circuit and put it and the VR3 in parallel.

Darlene

Will have to draw one ! Hopefully this week! Hud is working a dream...above water

27th November 2005, 19:17	#1 (permalink)
Pierre Farrugia Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: Malta Posts: 636	Vr3 + HUD connected to 1 cell !!!! Hello, Can someone explaine to me if I can connect 2 devices, eg a VR3 and a HUD circuit to one cell ? Has anyone tried this out ? Also in URI HUD he connected everything to the YBOD cells, can someone explaine to me how this can be done (not how to connect wires i.e. imparallel) but if additional resistors or circuits are nesessary not to effect the YBOD ? EG a VR3 works with one cell, the HUD I build works on 1 cell, can I just connect both to one cell ? My circuit uses the famous 10K across the sens and uses an opamp as a buffer as well! __________________ Pierre Farrugia My wife told me " If you don't quit diving I'm going to leave you" My reply " God, I'll miss you" www.atlam.org www.divemed.com
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27th November 2005, 20:30	#2 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,694	Re: Vr3 + HUD connected to 1 cell !!!! My Uri HUD is conected to all three cells using a loomb that just goes in series with the existing loom. Un plug ends from molex conectors plug into HUD blug HUD ends back into Molex. VR3 is linked into cell one through the HUD control box. Non crimping conectors are used. Resistors are used to buffer the circuit but I cant tell you how its done. Sufice as to say a total short o the HUD does not afect the readings on the hand sets. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System Last edited by Mark Chase : 27th November 2005 at 20:33.
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28th November 2005, 01:23	#3 (permalink)
Scuba_Vixen e/mCCR Dolphin Pilot Current Rebreather/s: Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: May 2005 Location: St. Croix USVI Posts: 557	Re: Vr3 + HUD connected to 1 cell !!!! Quote: (Originally Posted by Pierre Farrugia) Hello, Can someone explaine to me if I can connect 2 devices, eg a VR3 and a HUD circuit to one cell ? Has anyone tried this out ? Also in URI HUD he connected everything to the YBOD cells, can someone explaine to me how this can be done (not how to connect wires i.e. imparallel) but if additional resistors or circuits are nesessary not to effect the YBOD ? EG a VR3 works with one cell, the HUD I build works on 1 cell, can I just connect both to one cell ? My circuit uses the famous 10K across the sens and uses an opamp as a buffer as well! Since a VR3 is intended to be a "stand alone" load on a cell, it has a 10K ohm resistor accross the cell leads built in. The 10K ohm resistor is there to balance the temperature compensation network of the cell. If you connect 2 loads, each with a 10K resistor, the net effective resistance is then 5K ohms. That would introduce some inaccuracy in the cells output. The degree of inaccuracy would vary with temperature and PO2. If you don't use a 10K resistor accross the input of the op amp in the HUD circuit, ... Then.... Since the VR3 already has the 10K resistor, if you just connect the HUD in parallel with it, the cell won't see anything different than with just the VR3 ... If you should want to use the HUD, but not the VR3, then you'd need to put the 10k resistor back in it. It would be nice to see a schematic of the input stage of your HUD, but as long as you have an op amp as the load on the cell, it should have a decently high impedance. Just leave the 10K resistor out of the HUD circuit and put it and the VR3 in parallel. Darlene Last edited by Scuba_Vixen : 28th November 2005 at 01:26.
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28th November 2005, 13:04	#4 (permalink)
Pierre Farrugia Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Feb 2005 Location: Malta Posts: 636	Re: Vr3 + HUD connected to 1 cell !!!! Quote: (Originally Posted by Scuba_Vixen) Since a VR3 is intended to be a "stand alone" load on a cell, it has a 10K ohm resistor accross the cell leads built in. The 10K ohm resistor is there to balance the temperature compensation network of the cell. If you connect 2 loads, each with a 10K resistor, the net effective resistance is then 5K ohms. That would introduce some inaccuracy in the cells output. The degree of inaccuracy would vary with temperature and PO2. If you don't use a 10K resistor accross the input of the op amp in the HUD circuit, ... Then.... Since the VR3 already has the 10K resistor, if you just connect the HUD in parallel with it, the cell won't see anything different than with just the VR3 ... If you should want to use the HUD, but not the VR3, then you'd need to put the 10k resistor back in it. It would be nice to see a schematic of the input stage of your HUD, but as long as you have an op amp as the load on the cell, it should have a decently high impedance. Just leave the 10K resistor out of the HUD circuit and put it and the VR3 in parallel. Darlene Will have to draw one ! Hopefully this week! Hud is working a dream...above water __________________ Pierre Farrugia My wife told me " If you don't quit diving I'm going to leave you" My reply " God, I'll miss you" www.atlam.org www.divemed.com
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