Hi David,
I have posted the document we discussed.
Will look them over and see what we can suggest.

The LM1812 is an old device, have you checked availability.?

Download the free expressPCB & expressSCH programs.

E

 

Hi David,
Wind a small auto transformer, say on a RM10 ferrite core, as a step up transformer.
This PDF has info on winding etc.

E
BTW:
If you would like to confirm that I am conversant with depth sounders,
check the Information in my AAC Profile.

Hi All
I'm stuck on the output transformer.(I know very little about RF transformers)
I looked up rm10 stuff in farnell but they don't seem to sell a parts kit.
and I don't know what I need.

bit lost on this one.
Can someone give me an idea of what I need to do.

lets say if it's possible I'd like to wind this on a torrid core.(what core)
how many turns does this sort of 150khz Rf auto transformer need.
are we looking 10::30 turns or is 100::300 ?
what gauge wire?

the frequency is 150khz short burst pulse
the driving transistor is a irf520
the supply voltage is 12volts

here is the transducer spec
asa 150Khz Depth Transducer
Replacement depth transducer with 7m of cable.
• Supply voltage: 12V DC
• Power consumption: nominal 120mA
• Power output: 100w + pulse
• Operating frequency: nominal 150kHz
• Dimensions: Length Overall: 106mm, Face Dia: 38mm, Thread Dia: 16mm

Many Thanks

David

 

hi,
It appears that the RM10 is obsolete, but 'aliexpress' claim to stock the RM10.

https://www.aliexpress.com/item/4000333805183.html

You could purchase an equivalent EI type ferrite transformer.

This link explains the winding details,
https://www.homemade-circuits.com/h...late-ferrite-core-transformers-for-inverters/

E

 

hi,
It appears that the RM10 is obsolete, but 'aliexpress' claim to stock the RM10.

https://www.aliexpress.com/item/4000333805183.html

You could purchase an equivalent EI type ferrite transformer.

This link explains the winding details,
https://www.homemade-circuits.com/h...late-ferrite-core-transformers-for-inverters/

E

Hi Eric

thanks, is this the right sort of thing I need
Is it the right type of core

https://www.ebay.co.uk/itm/382420397224?hash=item590a082ca8:g:7ZwAAOSwrp9hp1b6
thanks again
David

 

Good Morning
I have been reading the this link
https://www.homemade-circuits.com/h...late-ferrite-core-transformers-for-inverters/
and found it very helpful.

I have a basic question though
So the output transistor is switching a 12 volt supply
the Transducer is a 12 volt transducer
So the output transformer is transforming 12 volts to 12 volts
consequently the input and output impedance of the transformer are the same.
So where is the impedance matching?

I surmise(guess) that the answer might be that the output "pulse" is not 12 volts but more like 30 volts and the transducer 12 volt rating is it's supply voltage not is operating voltage?
Now it would seem we have a 1:3 ratio and require 3 times the number of primary turns on the secondary.
ie primary 3 secondary 9

But this is not really impedance matching the output stage of the transistor with the input impedance of the Transducer
is just a step up transformer

What am I missing here?

thanks everyone

David
.

 

So the output transistor is switching a 12 volt supply
the Transducer is a 12 volt transducer
So the output transformer is transforming 12 volts to 12 volts
consequently the input and output impedance of the transformer are the same.
?

hi David,
So where is the impedance matching
Ideally, the Auto transformer inductance has to be resonant at 150kHz, with the ~700pF of the 7mtr connecting cable. [this is shown in my earlier sims]
Fine-tuning can be achieved by selecting capacitors across the 700pF or preferred by using the 'tuning' slug in the transformer.
Use 28 or 39SWG enamelled copper wire.
The primary and secondary are wound as a continuous winding, bring out a connection turn at the junction of the primary and secondary.

The primary inductance of the autotransformer should be 100uH and the secondary 900uH, so that is a 1:3 step up transformer.

12 volt supply the Transducer is a 12 volt transducer
So ideally the 12V primary voltage will be raised to ~36V on the secondary across the transducer.
See my sims for Power output.

The 1uF coupling capacitor from the transformer secondary to the transducer is optional, in some receiver systems it is required that the DC component, ie: +12V is blocked.

This will depend upon your receiver design, remember the important Timed Controlled Gain of the receiver is required,

E

 

hi David,
So where is the impedance matching
Ideally, the Auto transformer inductance has to be resonant at 150kHz, with the ~700pF of the 7mtr connecting cable. [this is shown in my earlier sims]
Fine-tuning can be achieved by selecting capacitors across the 700pF or preferred by using the 'tuning' slug in the transformer.
Use 28 or 39SWG enamelled copper wire.
The primary and secondary are wound as a continuous winding, bring out a connection turn at the junction of the primary and secondary.

The primary inductance of the autotransformer should be 100uH and the secondary 900uH, so that is a 1:3 step up transformer.

12 volt supply the Transducer is a 12 volt transducer
So ideally the 12V primary voltage will be raised to ~36V on the secondary across the transducer.
See my sims for Power output.

The 1uF coupling capacitor from the transformer secondary to the transducer is optional, in some receiver systems it is required that the DC component, ie: +12V is blocked.

This will depend upon your receiver design, remember the important Timed Controlled Gain of the receiver is required,

E
Thanks that's fantastically helpful. I have got a few of
RVFM A2-AR-10X100 100mm Ferrite Rod Aerial
apparently there 9-10 microROD ,I'll do some calcs and see if I can do some basic testing using them.
Hope to hook the generator to IRF520 and to the transformer this weekend.
I've got LTspice up and running again, I do a few tutorials and try and build a sim of what I'm trying to do.

Don't like the sound of "Timed Controlled Gain" sounds complicated.
thanks all
David

 

Don't like the sound of "Timed Controlled Gain" sounds complicated.

Hi,
Look up Voltage gain controlled OPA's.
E

 

Hi All

is there any reason why you can't or should not wind a autotransformer configuration on a Toroidal core?
for L1:L2 below(assuming you can physical get the right number of turns)

thanks

David

 

hi David,
It should be OK, make sure the core ferrite material specification is within the required operating frequency [ 150kHz]

E
BTW: it is the inductance values which are important, get the required number of turns from the toroid datasheet.


Update:
I would visit the local yacht Chandlers for an old/scrapped sounder, recover the transformer.

 

Hi All
Anyone know where I can get some cheap transducers (150khz) for testing the echo sounder, they don't have to go in the water
and some that would only work as a receiver would be useful.
this is just for some development testing.

The real thing is a bit pricey and I don't know how robust there are, If I mess up.
thanks

David

https://www.foxschandlery.com/nasa-...MIpq3yrtHy9QIVkN_tCh0dNA8WEAQYBSABEgKxbvD_BwE

 

Good Evening All

I finished building the 150khz transducer transmitter
using 2 555'ds and the driving circuit is a Nchannel irf520 module
and Eric output auto transformer configuration below.
I used FT140-43 FAIR-RITE FERRITE CORE TOROID RING with 24 swg 30 turns and 10 turns
it measured 900uh and 100mh on my component tester(not super accurate)

the output voltage at the input to the transducer cable is around +/- 120volts
it's a little bit noisy, I'll post a scope output later.

The main problem I seem to have is the duty cycle of the 150khz pules has changed from 50 percent at the input to the
irf520 module to about a 5% spike going to the transducer.
And consequently there is no output from the transducer, It looks like I've effectively PWM to zero power.

any idea's what to check?

thanks all
David H

 

The main problem I seem to have is the duty cycle of the 150khz pules has changed from 50 percent at the input to the irf520 module to about a 5% spike going to the transducer.

hi David,
What do you see on the Scope for the Vxdr voltage at the transducer, it should almost be a Sine wave at 150kHz if you have the circuit tuned correctly, [C2] not a 5% spike.
Scope the Drain of the MOSFET, what do you measure.?

E

 

hi David,
What do you see on the Scope for the Vxdr voltage at the transducer, it should almost be a Sine wave at 150kHz if you have the circuit tuned correctly, [C2] not a 5% spike.
Scope the Drain of the MOSFET, what do you measure.?

E

hi David,
What do you see on the Scope for the Vxdr voltage at the transducer, it should almost be a Sine wave at 150kHz if you have the circuit tuned correctly, [C2] not a 5% spike.
Scope the Drain of the MOSFET, what do you measure.?

E
Hi All
the duty cycle looks ok now, Don't know what I saw before!!
both scope channel are on 20 volts and probes on X10
blue trace is the cmos drain
red is across the transducer
looks like +30 to +40 volt peak on the drain
and +/- 45 on the transducer

the supply voltage for the transducer is 2 pp3 both pretty flat,
will connect to 12 volt bench supply and try again

thanks

David

 

hi David,
I would try reducing the Pulse on time by about 50% while observing the transducer signal.
Keep the 555 running at 150kHz, just change slightly the mark/space ratio.

E
BTW: are you powering the 555 from 5V or 12V, a 12Vgate drive signal will switch the IRF MOSFET harder on.
The C3 cap should be as shown in this clip, not as shown in post #52 [ drawing error]

 

Good Evening All
I attached a bench power supply to irf mosfet module.(picture below)
If I turn it up beyond 10.5 volts the whole thing oscillates at +500khz(there is quite a bit of noise on the drain(red trace)
any ideas where that is coming from?
the 555's are running off pp3(flat pp3's about 8 volts).
How do I tune the auto transformer ?
I have a Farnell DSG1 100khz VFO / signal generator which if I full wave rectify I get a half tidy up to 200khz sine wave from.
can I run this into the gate of the mosfet amp with continuous 150khz with the transducer and auto transformer etc hookup up without frying the transducer? Or should I tune using the pulse generator
How about if I drop supply voltage to the msofet module to a couple of volts?
I'll change the capacitor to 47uf 400volts I have a 220uf 16volt electrolytic in there at the moment, I did not think this reservoir cap was critical
R1 is 10 ohms
I try reducing the pulse on time from 130us to 70us like you suggest(why ?)

learning plenty from all this, thanks everyone David

 

I try reducing the pulse on time from 130us to 70us like you suggest(why ?)

Hi,
Where did I say 130us to 70us.?
I said, Pulse on time by about 50% while observing the transducer signal.
Which is half Period of 150kHz is 3.33uSec/2 ie: ~1.7uSec.

A 150kHz signal has a Period of 6.666’uSecs, so half period is 3.333’uSec, so why did you initially choose 130uSec, which is about 7.7kHz????

On the posted Scope image, why is the Drain voltage only approx 1.5V.??
Look at this marked up image.

Why did you use a 220uF in that transformer connection.?

can I run this into the gate of the mosfet amp with continuous 150khz with the transducer and auto transformer

That would not be a good idea.

I need to see a circuit diagram and photo shot of your circuit layout, ref the 500kHz osc problem.

E

 

he 555's are running off pp3(flat pp3's about 8 volts).

That could be the cause of the problem oscillation, if the PP3s can't source/sink enough current to drive the FET gate capacitance and ensure the FET switches on fully.

 

Hi,
Where did I say 130us to 70us.?
I said, Pulse on time by about 50% while observing the transducer signal.
Which is half Period of 150kHz is 3.33uSec/2 ie: ~1.7uSec.

A 150kHz signal has a Period of 6.666’uSecs, so half period is 3.333’uSec, so why did you initially choose 130uSec, which is about 7.7kHz????

On the posted Scope image, why is the Drain voltage only approx 1.5V.??
Look at this marked up image.

Why did you use a 220uF in that transformer connection.?

can I run this into the gate of the mosfet amp with continuous 150khz with the transducer and auto transformer

That would not be a good idea.

I need to see a circuit diagram and photo shot of your circuit layout, ref the 500kHz osc problem.

E

Hi Eric
miss understood
" I would try reducing the Pulse on time by about 50% while observing the transducer signal. "
I thought you meant the burst length.
I'll drop the duty cycle of the 150khz as you suggest and watch the transducer.
I used 220uf because of circuit below and I did not think it was critical.
I'll tidy stuff up this weekend and post some photo
both scope probes are on X10 so voltage is around 15 volts

thanks all for your help.
I'll power the 555's from the bench supply as well

 

hi David,
As the project is powered by +12Vdc I would also power the 555 timer with 12V, as this will give the best possible voltage drive to the IRF540 Gate.
The Transmit Period is how long the150kHz drive is applied to the IRF Gate, also known as the Key pulse.
It is usually between 150uSec and 500uSec, depending upon the depth you are trying to measure.

One simple method of measuring the actual power at the transducer is to add a 1R resistor in the ground return path of the transducer and measure the voltage/current across the 1R. [Using a Scope]

E

Added:
Plot showing the effect of setting the IRF Gate pulse ON pulse to 1.7uSec [ rather than 6.6666uSec/2]
So on your 555, have some method of trimming the Freq [nominal 150kHz] and the High out period [nominal 1.7uSec] at ~12Vdc

BTW: Note on R4[transducer] 'ringing' after the drive stops, at about 550uSec, it rings for about 200uSec.
During this ringing period, you will not be able to measure depths. [it may ring longer on your project].

Your receiver circuit will have to limit and block these signals from reaching the receiver output, if you plan to digitize the Echo depth from the received Echo.