Replies to Minipulse Plus

[Altra]

That could be an alternative, but you would need to measure the drop-out voltage.

Don't know the drop-out voltage? But I have used the ICL7662 with 7 cell nimh packs without problems. The ICL7660's would fail for me, even when used at 9.6V. That is when I searched out the ICL7662.

[Qiaozhi]

@Davor

If you can find a ICL7662, same chip but 20V tolerant

That could be an alternative, but you would need to measure the drop-out voltage.

[Qiaozhi]

@ Qiaozhi, I can only get ICL7660A and it separates from its smoke at 13V. I'll figure it out.

The problem with the ICL7660A is that it's operating range is up to 12V input, but with an absolute maximum rating of 13.0V. Otherwise, it can be permanently damaged (smoke test). With a new set of 8xAA cells the battery pack can reach 12.88V (which is close), and when used as a voltage inverter it drops out at 10.5V (which is 1.31V per cell). If you opt for rechargeables, then 8 cells will only provide 9.6V. This means you need to use 10 cells, and the battery pack voltage will be a nominal 12V. Unfortunately it's not as simple as that, because rechargeables (immediately after charging) have a much higher voltage that can get above 1.3V per cell, and then ... bang!

This is why I prefer the LT1054, with an operating range up to 15V, and (when used as a voltage inverter) it doesn't drop out until 8.4V (1.05V per cell).
Also, the LT1054 provides much lower voltage losses than the ICL7660A.

[Altra]

@Davor

If you can find a ICL7662, same chip but 20V tolerant

@Jose

Goldscan 5 uses cd4066's with a capacitor diode level shifter

see post 146, schematic posted by Geo

http://www.geotech1.com/forums/showthread.php?6965-LOOKING-FOR-GOLDSCAN-4-Schematic&p=162575

[Davor]

If I understood you correctly, you wish to replace the FETs with 4066 switches in your GS4. Unfortunately it is not possible without corrections to the power supply to 45028, and a level shifter for their signal input.
You could add 100k resistors in series with the FETs' gates that would force them to behave.

@ Qiaozhi, I can only get ICL7660A and it separates from its smoke at 13V. I'll figure it out.

[Jose]

Hello everyone.
I want to replace the transistors channel field effect "N" on my GS4 homemade, built by 4066.
I have several questions, about feeding the 4066., Ie with (+5 and -5) or (+12 and -12).
Same question for the time base, composed of integrated 45038, (+5 and -5) or (+12 and -12).
E seen different configurations in the forum,
I have a partial outline, made of Dip Trace. I appreciate any help.
Jose

[Qiaozhi]

I'll go with ICL7660. It is synchronised via 1k resistor, and no pull-ups to pin 6 as with LT1054. So I'll keep R9, but at 1k, and I omitQ2 and R5, and C3/C5 will get beefed up. It must work.

The ICL drops out at 10.5V, and there are issues with the maximum input voltage as well. A better solution (IMHO) would be to use a PIC to generate the TX pulse and sample delays, while at the same time driving the LT1054 with a 25kHz equal mark-space ratio sync pulse.

[Davor]

I'll go with ICL7660. It is synchronised via 1k resistor, and no pull-ups to pin 6 as with LT1054. So I'll keep R9, but at 1k, and I omitQ2 and R5, and C3/C5 will get beefed up. It must work.

[greylourie]

A few thoughts ... For a revision D (or whatever comes next) I'd like to see PCB placers for:
- a 10k resistor between U8 pin5 and GND - this will allow for using bipolar op amps at this place as well, and does not hurt performance in case of a FET op amp
- 100k resistors in series with Q3 and Q4 gates - I'll fit those "Ikebana style" on a Rev B PCB
- a 47pF capacitor can be added in parallel with R22 to stop propagation of switching glitches back to the feedback network.

I think with a good bipolar op amp that does not produce too much noise, and has a decent common mode range, the input gain could be reduced, the integrator stage gain could be increased to compensate, and the sampling could commence a bit sooner. Choice of well designed bipolar op amps is much wider than in case of FET op amps. There is no problem omitting any of these additions or replacing them with jumpers.

Replacing FETs with a bilateral switch seem a good idea. Eric recommended them as well. Small trouble is that in case of Minipulse it would require ±5V supply in a switching logic to power these properly. I can fix this on a Gb board

He mentions it in the image in first post here : http://www.geotech1.com/forums/showt...354#post171354

Like Qiaozhi says, this brilliant project could possibly spawn future advanced models. Replacing J113's is something I thought of with the GS4. Turns out Orbit was few years ahead, with his "Hibrid". A minipulse plus board, in combination with a +/-5v based logic board, would be a logical progression. Minipulse plus could be used as basis to inspire fast low power CS6-like designs. Or something with a bit more "oomph".

As it stands, it is perfect for novices like me. Looking forward to see the completed build thread once it goes up.

[Davor]

J113 is a classic.
"Can't beat the classic" - Jason Statham - The Expendables 2

I prefer BF245B though. Small, cheap, fast, symmetric.
But Qiaozhi is right, I can have a complete switching solution for Minipulse GB with a single 4066, and no diode OR-s.

[ivconic]

The MPP will probably not change drastically from what it is now, and any future revisions will only incorporate small evolutionary fixes to correct potential errors or make small improvements.

Additions such as GB, and bipolar opamps with various optional components, etc., can be incorporated in a more advanced version (Minipulse Super Plus?).

I did read somewhere where Eric suggested that bilateral switches were a better alternative to FETs. However, the J113s have the advantage of taking up minimal PCB real estate, and make routing easier. Bilateral switches probably make more sense in a GB-enabled MPP where you can make use of all 4 switches in the package. Also, I notice the CS6 PI (which is one of Eric's more modern designs) continues to use FETs.

CScope simply loves FETs, especially J113!
Hard to come by... expensive too!
MPP... any video so far?

[johnandles]

That was fast

Ozzies in the lead so far......"Ozzy Ozzy Ozzy.....!"
Lol

[Qiaozhi]

A few thoughts ... For a revision D (or whatever comes next) I'd like to see PCB placers for:
- a 10k resistor between U8 pin5 and GND - this will allow for using bipolar op amps at this place as well, and does not hurt performance in case of a FET op amp
- 100k resistors in series with Q3 and Q4 gates - I'll fit those "Ikebana style" on a Rev B PCB
- a 47pF capacitor can be added in parallel with R22 to stop propagation of switching glitches back to the feedback network.

I think with a good bipolar op amp that does not produce too much noise, and has a decent common mode range, the input gain could be reduced, the integrator stage gain could be increased to compensate, and the sampling could commence a bit sooner. Choice of well designed bipolar op amps is much wider than in case of FET op amps. There is no problem omitting any of these additions or replacing them with jumpers.

Replacing FETs with a bilateral switch seem a good idea. Eric recommended them as well. Small trouble is that in case of Minipulse it would require ±5V supply in a switching logic to power these properly. I can fix this on a Gb board

The MPP will probably not change drastically from what it is now, and any future revisions will only incorporate small evolutionary fixes to correct potential errors or make small improvements.

Additions such as GB, and bipolar opamps with various optional components, etc., can be incorporated in a more advanced version (Minipulse Super Plus?).

I did read somewhere where Eric suggested that bilateral switches were a better alternative to FETs. However, the J113s have the advantage of taking up minimal PCB real estate, and make routing easier. Bilateral switches probably make more sense in a GB-enabled MPP where you can make use of all 4 switches in the package. Also, I notice the CS6 PI (which is one of Eric's more modern designs) continues to use FETs.

[silverdog]

my mistake, I will be providing pins and plugs for PL1-5

So far both +5 & -5 volts works ok, I must admit I am not too keen on the tiny solder pads.

If you have the kit no plugs or pins are provided for PL 1-5, you need a trip to your parts store
here is a tip, if you want plugs with wires have a look in your R/C model shop for servo leads.

[Davor]

A few thoughts ... For a revision D (or whatever comes next) I'd like to see PCB placers for:
- a 10k resistor between U8 pin5 and GND - this will allow for using bipolar op amps at this place as well, and does not hurt performance in case of a FET op amp
- 100k resistors in series with Q3 and Q4 gates - I'll fit those "Ikebana style" on a Rev B PCB
- a 47pF capacitor can be added in parallel with R22 to stop propagation of switching glitches back to the feedback network.

I think with a good bipolar op amp that does not produce too much noise, and has a decent common mode range, the input gain could be reduced, the integrator stage gain could be increased to compensate, and the sampling could commence a bit sooner. Choice of well designed bipolar op amps is much wider than in case of FET op amps. There is no problem omitting any of these additions or replacing them with jumpers.

Replacing FETs with a bilateral switch seem a good idea. Eric recommended them as well. Small trouble is that in case of Minipulse it would require ±5V supply in a switching logic to power these properly. I can fix this on a Gb board